OF REDLANDS, CALIFORNIA  - Founded 24 January 1895

4:00 P.M.

May 14, 1998

Meeting # 1604

The Lure and Lore of Gemstones

by Stanley D. Korfmacher M.D.

Assembly Room, A. K. Smiley Public Library


Though not a graduate gemologist, Stanley D. Korfmacher M.D. has studied gems and minerals well over twenty years. He has subscribed to Gems and Gemology, the respected GIA publication, for twenty years.

He was born on December 7, 1931, in Grinell, Iowa. His father was Edwin Korfmacher M.D., F.A.C.S. and his mother was a registered nurse.

He graduated from Carleton College in 1953 and from Northwestern Medical School in 1957. Subsequent training included internship at Swedish Hospital in Seattle, and the Lahey Clinic in Boston from 1958 to 1961. From 1961 to 1963 he served as a physician with the U.S. Public Health Service. He was Assistant Chief of Medicine at San Francisco Marine Hospital.

As a specialist in internal medicine he practiced at the Beaver Medical Clinic in Redlands, California, from 1963 to 1994.

Some know him as an antiquarian, classical clarinetist, mineral collector, art collector (especially art glass and Art Nouveau), auto buff, and owner of five dogs. He was a founding member and 1st clarinetist in the Fourth of July Band for 16 years. He is the Chairman of the Redlands Cultural Arts Commission, President of the Spinet Music Club, and is on the Boards of the Redlands Symphony, and the Redlands Conservancy.

For 12 years he has been one of the supervisors of the Medical Museum of the San Bernardino County Medical Society and he heads that subcommittee of the Historical Committee.


The Lure and Lore of Gemstones is an attempt to administer a concentrated dose of gem knowledge, distilled from twenty books, and represented on less than twenty printed pages.

The Lure and Lore of Gemstones

Gemstones have been prized by nearly all cultures worldwide since the dawn of civilization, and even before, since we find ornamental minerals in the burial sites of primitive man. They are the stuff of legend. As Paul Desautels, the late curator of gems and minerals at the Smithsonian, has written: "Continents have been explored, wars fought, crimes committed, fortunes made and lost, all in the pursuit of these uncommon bits of minerals"2. In addition, many gemstones have had religious, talismanic and medicinal significance at times in the past, all apart from their beauty and economic values. Even today the New Age people continue those traditions. Large gemstones and royal jewelry have denoted wealth and power over the ages, and of course they are the ultimate portable and concealable wealth. But it is as objects of beauty that most people enjoy gemstones.

This paper is an attempt to give a concise overview of the world of gemstones and an introduction to the gemology of most of the important ones and some of the uniquely beautiful "collector" stones which are unknown to the general public.

I will start by defining the term "gemstone". Most authorities agree that there are three major criteria: beauty, durability and rarity. Beauty is paramount. There are a number of gems which are easily damaged, but are unquestioned gemstones because of their unique beauty and the lack of a suitable substitute. The importance of rarity is variable; quality amethyst was rare and as expensive as rubies and emeralds until the huge finds in Brazil and Uruguay in the late 1800's brought prices down drastically.15,18 On the other hand, extreme rarity often combined with erratic supply reduces the marketability of a gemstone3 and prices are lower than one would expect, (unless one is dealing with a red diamond!).

I would add a fourth criterion, namely a long history as a gem material. Such unquestioned gemstones as amber, turquoise, carnelian, coral, jasper, pearl and lapis lazuli might not make the cut if they had not been treasured for thousands of years by every culture which knew them. This list also brings up the point that not all gemstones are minerals. Amber is the hardened sap of pine trees which lived millions of years ago and hence it is organic. Coral, shell, pearls and ivory are all natural materials of animal origin, though they consist largely of the related minerals calcite, aragonite and hydroxy calcium phosphate. Glass has been used in jewelry and art objects since antiquity; as itself, as faence in ancient Egypt, as enameling and cloisonné, and as "lead crystal" (called 'paste' in the jewelry trade until recently). Perhaps all these substances should be called gem materials rather than gemstones.

Another point I would like to make is the uselessness of the terms precious and semiprecious. These terms should be abandoned.3 For many years diamond, ruby, emerald, sapphire, pearl and opal were the precious gemstones, defined as "of great value or high price", while semiprecious stones were "of less commercial value" However, a number of the other gemstones may equal or exceed 99% of diamonds and the other so-called precious stones in value when they are top quality, for example alexandrite and emerald-green imperial jade may bring up to $10,000 per carat. Many others are in the $500 to $2,000 per carat range of commercial diamonds, rubies, sapphires and black opals. Examples are imperial topaz, demantoid and tsavorite garnet, and rare paraiba tourmaline.14, 15

I shall now discuss the criteria of beauty in gemstones, a dangerous task in view of the varying factors from one variety to the next and the subjective nature of these factors. Color is of prime importance. In most diamonds, the ideal is total absence of color, and beauty is determined by brilliance and the fire of spectral dispersion which depend on the clarity of the stone and the quality of the cutting. In colored diamonds, the more intense the color the better, especially the yellow stones. In colored gemstones, it has been found by both long experience and by scientific testing that most people prefer colors close to pure primary colors, thus pure green and pure yellow are preferred to greenish yellow and pure red is favored over orange-red or purplish red, pure blue over purplish blue or slightly greenish blue. These color choices are reflected in the prices of the cut stones. There are exceptions-amethyst purple and slightly bluish green emeralds and tourmaline are favored colors and the pinkish orange of 'padparadscha' sapphire and 'imperial' topaz are highly prized as well. At the bottom of the list are the greenish browns.

The so-called phenomenal stones, named for their optical phenomena, depend for their beauty not only on color but the degree and perfection of their special effects. The star stones should have sharp and even 'legs' well centered on the stone. Some star stones have four rays while rubies and sapphires have six. Catseyes have a single band. All are due to the crystal structure oriented parallel inclusions of fine needle-like crystals of another mineral such as rutile or tiny hollow parallel tubes layered in the gem. Moonstones have adularescence, a more diffuse band of brightness, blue in the best stones, multicolored in the rare rainbow moonstones. Labradorite has 'schiller' highly directional bright color, often blue but also yellow and purple. Opals have 'play of color' with one, two, three or all spectral colors. Their beauty and value depend on the brightness and pattern of the color flashes, the pleasing contrasts of the colors and the absence of 'dead areas' as well as the ground color of the opal, black, white or crystal.

Another criterion of gemstone beauty is brilliance. Gemologically speaking, brilliance is not used as a term for surface luster, which has its own lexicon---metallic, submetallic, adamantine(diamond-like), vitreous(glassy), and resinous(greasy). Brilliance depends upon three things; the color and clarity of the gem material and internal reflection at gem-air interfaces. The brilliance of reflection depends on the angle at which the reflection occurs, the refractive index and the quality of the cutting. Each transparent gemstone has its own ideal angles for the facets giving maximum reflectance of the light entering the gem from above. Gemstones with a low refractive index such as the quartz stones amethyst and citrine frequently show a 'window' where one looks through the bottom of the stone instead of seeing reflected light. This occurs when the stone is too shallow to allow the proper angles to be used or when the cutter is inept. The depth of color is a factor in brilliance as well; for example, a sapphire which is too dark can never be very brilliant. As mentioned before, clarity is also important; an emerald which is full of inclusions and internal fractures loses brilliance, and a sapphire with too much 'silk' looks hazy and less attractive.

A third aspect of beauty applies mainly to colorless or lightly colored stones, and that is dispersion, the ability of the gemstone to spread rays of white light into the full spectrum of rainbow colors with many facets acting like tiny prisms. These color flashes, called 'fire' account for much of the beauty of diamonds. They are also important in a few colored stones with high dispersion such as light green damantoid garnet and benitoite, the California gemstone, when it is light to medium blue or colorless. Too much dispersion can actually be detrimental to beauty as can be seen in the 1960's strontium titanate and rutile diamond substitutes which appear too gaudy compared with diamonds or cubic zirconia.4 Some natural collector stones e.g.. sphene (green) and sphalerite (orange) have up to four times3 the dispersion of diamonds but it is usually subdued somewhat by the body color.

We will move on from the aspects of gemstone beauty to the qualities which determine durability. There are three which are most important; hardness, toughness and chemical stability.

There are many scales of hardness, but the most used is the oldest, the simple Moh's scale dating from 1820.

Moh's Scale of Hardness

1. Talc  
2. Gypsum Alabaster, soapstone
Fingernail 2 1/2
Ivory 2 1/2 - 3
3. Calcite Gold, silver, copper, marble, bone
4. Fluorite Bronze, lead 'crytal' (glass)
Platinum 4 - 4 1/2
Common glass 4 1/2 - 5
Apatite Iron, tooth enamel (hardest substance in human body)
6. Fledspar Steel knife blade, Tool steel 6 1/2 - 7
7. Quartz Steel file, concrete*, granite*
Garnet sandpaper 7 1/2
8. Topaz  
9. Corundum Silicon carbide abrasive paper, cloth, grinding tools, drills
10. Diamond  
  * contains quartz

Each substance will scratch the ones lower in number and be scratched by those higher. I have added common substances on the right for comparative purposes. It is obvious that a gemstone should have a minimum hardness of 7 to avoid being scratched by casual contact or hard rocks. Indeed, house dust contains quartz dust and so do most paper towels and tissues which might be used to wipe a gemstone. However, there are several gemstones of unique beauty which are much softer, such as amber (2.5), pearl (2.5-4.5), turquoise (5-6), and Opal (5.5). These must be worn with care, and also cleaned carefully. Amber is saved from damage to some degree by its light weight; amber will actually float in salt water. It is also easy to repolish.

Toughness is as important as hardness. Gemologically, it is the opposite of brittleness. Frequently hard substances are also brittle, and this is true of many gemstones, decreasing their durability. Some softer stones, such as opal, are also brittle and hence fragile. Fortunately diamond is moderately tough as well as being very hard. The prize for toughness goes to jade, which has interlocking microscopic fibers. A solid jade boulder cannot be dented or broken by a sledgehammer. A ring set with jade can be thrown against a stone or a cement wall with little or no damage to the stone. Jade can be carved more finely than any other material because it is so tough. At the other extreme are stones like zircon, harder than jade or quartz but so brittle that a faceted stone in a ring will soon show many small chips if worn regularly. Somewhat related to brittleness is the presence or absence of cleavage planes. Some gemstones have this disability of easy parting when struck at a certain angle. A few will cleave in two or three directions. Topaz has a very easy cleavage in one direction, and stones must be cut and set with this in mind. Diamonds cleave less readily but a blow on a diamond in an exposed setting may split the stone in two. Cleavage is used to break large diamond crystals to avoid prolonged sawing. The corundum stones (ruby and sapphire), spinel, tourmaline, and garnets have no cleavage and beryl (emerald and aquamarine, etc.) has only indistinct cleavage.

The third major determinant of durability is chemical stability; the ability to resist attack by strong acids, alkalis, solvents, heat, light and the passage of time. Since most of the major gemstones are resistant to most of the agents just listed, I shall mention only a few of the prominent problems. Pearls are damaged by acids, even relatively weak acids such as lemon juice (citric) and vinegar (acetic) and household cleaners (oxalic). Shell cameos would also be attacked. Hot, dry air is also hard on pearls. Amber is damaged by lye and ammonia and can be burned. Turquoise is damaged by ammonia, strong detergents, soap and oxalic acid. Due to porosity, it can be discolored by oils and grease. Opal is also porous and can be damaged by sudden temperature changes and changes in hydration. It is also attacked by strong alkali solutions. Rose quartz, pink beryl (morganite) and lavender spodumene (kunzite) all fade in prolonged strong light. It is said that color can be restored by gamma radiation. Emeralds frequently have internal fractures and cavities containing liquid or gas. If a jeweler attempts to use steam cleaning, they may literally explode or shatter. The same is true of other stones which have inclusions. Diamonds can be burned in a hot house fire, but this is uncommon; a jeweler's torch can also damage diamonds.

Each of the major categories of gemstones will now be discussed.

I. Diamonds:

Diamonds combine supreme hardness, moderate toughness, a high refractive index and high dispersion to give us by far the best colorless gemstone and, in the form of "fancy" naturally colored diamonds, a rare few of the finest colored stones as well. Diamonds form in molten rock between 75 and 120 miles beneath the surface of the earth in the asthenosphere, at temperatures of 1000 to 2000 degrees C. and pressures of 40 to 70 kilobars (70,000kg/cm ).6 All natural diamonds are billions of years old. They arrive at the surface by volcanic eruptions in a conglomerate rock, usually kimberlite (lamproite in Australia). Many diamonds never make it - if convection currents swirl them deeper into the magna, they revert to free carbon atoms; if they cool slowly as they rise, they transform to graphite; if they contact oxygen while hot, they vaporize into carbon dioxide. Only if they blast to the earth's surface and cool rapidly do they survive as diamonds.7 Thus only one in a hundred kimberlite pipes have enough diamonds to be mined. Alluvial deposits, where diamonds have washed or been pushed by glaciers hundreds or even thousands of miles from pipes to riverbeds and even the ocean, are found in India, Brazil and western Africa.

Mined in India since 400 BC (and possibly as early as 1000 BC),6 they were unknown in Europe until the 1300's, and then only as uncut octahedral crystals (where we get the term diamond-shaped) In the mid-1600's the famous gem merchant Jean Baptiste Tavernier made six trips to India. He was the first European allowed to see the treasures of the Mughal emperor. He brought back 44 large cut diamonds and 1122 smaller ones, including the 112 carat Great Blue, part of which became the Hope Diamond, and the Koh-i-noor, now in the Queen's Crown of England. Tavernier's best customer was the Sun King, Louis XIV of France, who had a passion for diamonds, and adorned himself with hundreds of them.6

In 1727, new finds in Brazil became the main source of diamonds as old mines in India declined.

In 1866, a 15 year old boy in South Africa, Erasmus Jacobs, found a 21 carat rough diamond sparkling in the sunlight on a riverbank. The boy's mother gave it to a family friend named Van Niekert, who loved minerals but had never seen a diamond. Later, Dr. Atherstone, a physician and amateur mineralogist, confirmed that it was a diamond. It was purchased by the governor of Cape Colony for 500 pounds and later cut in London into a diamond of 10.73 carats and named the Eureka. After a succession of owners it was acquired by Harry Oppenheimer, chairman of DeBeers and returned to Cape Town 100 years after its discovery. It is now on display in the House of Parliament.6

Strangely, the first diamond found caused little excitement, but the second resulted in a diamond rush. It was also found on the surface, sparkling in the sun, by a Griqua shepherd named Booi who was driving his sheep in the Hometown District. That evening he offered to trade the stone for a night's lodging with a local farmer named Duvenhage who was not interested. "Go to Schalk Van Nierkerk" he said. "He likes stones, I don't". Van Nierkerk lived nearby so Booi went there and offered his stone to the same man who had been given the first diamond found! This time he had no doubts. When he asked the price, Booi replied "Sir, whatever you wish". Without hesitation Van Nierkerk offered him all he possessed, 500 sheep, 10 oxen and his horse. Booi left the next morning with all his new possessions. A few days later in Hopetown, the diamond was found to weigh 83.5 carats and Van Neirkerk received 11,300 pounds for it. It was cut to 47.74 carat pear shape and sold to the Earl of Dudley for $125,000. In 1974 it was auctioned at Christie's in Geneva for $552,000.6

In January 1905, an African worker at the Premier mine near Pretoria found a huge diamond crystal, 4 inches long, 2 inches wide and 2 1/2 inches deep weighing 3100 carats. It was, and is, the largest diamond ever found. A cleavage plane on its largest face indicates it was part of a larger stone, but the other part was never found. It was named the Cullinan after Sir Thomas Cullinan, who discovered the mine and was president of the mining company. The Transvaal government purchased it for $750,000 and presented it to King Edward VII on his birthday. Amid a show of elaborate security precautions, a box containing a fake stone 5 was sent to London while the Cullinan was sent by unregistered5 parcel post with a 3 shilling stamp! The king at first wanted to keep it uncut, but the famous Asscher brothers of Amsterdam, the finest diamond cutters in the world, convinced him otherwise. The Royal Navy provided a powerful escort for an empty box taken across the North Sea while Abraham Asscher, with the 1 1/3 pound crystal in his pocket, traveled to Holland incognito by train and night ferry.6 The Cullinan was cut into 105 stones; the largest four remain in the British crown jewels, with Cullinan I, at 530 carats the largest cut diamond in the world, residing in the Imperial Scepter.

Other diamond locales have been found in Africa: German Southwest Africa (now Namibia) in 1908 by railroad workers; Belgian Congo in 1914; Sierra Leon in 1930; Ghana and others more recently. Russia has become an important diamond source in recent years and produces stones of exceptional color and clarity. The large Siberian deposits were not found until 1953, but within 20 years the Soviet Union became the second largest industrial producer after Zaire and the second largest gem diamond producer after South Africa. Australia has become a unique diamond source even more recently. The Argyle mine in Western Australia is the world's best source for "champagne" and "cognac" and pink diamonds and the only source for deep pink diamonds. It opened in 1986 and mines about 40 million carats per year, the world's largest volume. Only one in 90,000 is pink.7 Canada shows great promise as a future diamond producer.

The marketing of diamonds is a story by itself.6 In the 13th century Marco Polo mentioned the Persian city of Hornuz as the most important market for precious stones, notably diamonds, coming from India. From there they went to Aleppo on the way to Constantinople and then to Venice. Venice had an exclusive relationship with the Muslim rulers of Aleppo and was the primary link between Europe and the East for over two centuries until Vasco da Gama's voyage opened the direct maritime route between India and Lisbon. Venice had a monopoly in the diamond trade and quickly developed the art of diamond cutting. Southern German cities and Bruges had close relations with Venice and also became diamond centers in the 1400's. When Bruges' harbor silted up, trade shifted to Antwerp, and when Portugal supplied rough diamonds from India in quantity to Antwerp it became a great cutting center. Most of the diamond cuts used today originated in the 1500's. In the 1600's political and religious pressures pushed many diamond cutters to Frankfurt and Amsterdam and after the Thirty Years War Amsterdam had a virtual monopoly which lasted for a century. England took over from the Dutch in India by 1700 and the Dutch then invested heavily in the new mines in Brazil. Antwerp, Amsterdam and London remain the principal European diamond markets.

Diamonds are valued by the four C's - color, clarity, carat weight and cut.

Color grading has become much more open in recent years as the system used by the Gemological Institute of America has taken over from the old and arcane terms Wesselton, Jager, Crystal and Cape. The GIA system starts with D (to avoid confusion with an other older system which used A, B and C). D is colorless; faint yellow tints become definite at K and value declines more rapidly until it rises again nearing Z, fancy intense yellow. Grading is aided by sets of standard stones, either diamonds or cubic zirconia. In the past few years a new system for grading colored diamonds has come from the GIA using such terms as "fancy intense purplish pink" and based in part on instrument readings.

GIA Color Grading Scale

D E F Colorless
G H I J Near colorless
K L M Faint yellow
N O P Q R Very light yellow
S T U V W X Y Light yellow
Z Fancy yellow

Clarity is defined by a GIA scale of eleven divisions.

GIA Clarity Grading Scale

F Flawless
I F Internally flawless
V V S 1 Very very slight inclusions
V V S 2 Very very slight inclusions
V S 1 Very slight inclusions
V S 2 Very slight inclusions
S 1 Slight inclusions
S 2 Slight inclusions
I 1 Imperfect
I 2 Imperfect
I 3 Imperfect

Carat weight goes back to the weight of a carob seed in ancient India. It is now defined as one fifth of a gram. For comparison, either a dime or a penny weigh about 12 carats. Jewelers divide carats into 100 points, so a quarter carat stone is a 25 point stone.

Cut refers not only to shape but to proportions, quality of faceting and perfection of polishing. The round brilliant cut is favored over marquise, pear, oval or emerald cut, all other things being equal. Facets must be sharp and even. The girdle must be neither too thick or too thin. The crown and pavilion must be in proper proportion to meet at the correct angle for greatest brilliance. Even the best cut is a compromise, however, between maximum brilliance and maximum fire; that is, between maximum reflection and maximum dispersion. Some authorities question the most modern cuts which favor brilliance over fire as opposed to the older European cuts which favor fire and also show flashes over a wider viewing angle.

The price per carat increases with diamond weight since large, clear, colorless crystals are very rare. Tiny diamonds sell for 10 to 20 dollars a point while a one carat diamond will cost from $400 for an off color and/or highly included stone to $10,000 or more for a D color flawless stone. A 10 carat D flawless might sell for $50,000 a carat. Colored diamonds can command even higher prices. A 3.14 carat Argyle pink sold for $1.65 million and a 0.95 carat red sold for $926,316 per carat or $880,000.13

No discussion of diamonds could be complete without the fascinating history of one of the great diamonds from ancient India.2, 6, 7, 14

Tavernier sold the Great Blue Diamond from India to Louis XIV in 1669. Louis lived another 46 years; his reign was one of the longest in history. No bad luck so far! In1672 the 112 carat Great Blue was recut into a 68 carat heart shape. Later, mounted into a pendant along with a great ruby, it was stolen during the French Revolution in 1792 by a man named Cadet-Guillot who fled to London with it. The French Blue was probably recut in Amsterdam around 1800 by Wilhelm Fals. Fals' son Hendrick stole the stone from his father, who died of grief shortly after, prompting Hendrick's suicide. Somehow the stone got to England. The recut stone, 44 carats, was shown to gem expert John Mawe by London jeweler Daniel Eliason. In the first, 1813 edition of Mawe's Treatise on Diamonds and Precious Stones the blue diamond is described as "superlatively fine" and "matchless". In the second edition, he said it was valued at 30,000 pounds and belonged to King George IV. A portrait of George IV by Sir Thomas Lawrence shows him wearing the Order of the Golden Fleece with a stone set above the symbolic dead lamb which bears a striking resemblance to the Hope. However, the diamond was still in Eliason's possession when he died in 1824 and in 1830 his heirs or successors sold the stone to prominent banker Henry Philip Hope. Hope was a collector of colored diamonds; an 1839 catalog of his collection gives detailed listings of 50 diamonds, 36 of which are colored diamonds weighing 30 carats or more, and one of these is the diamond we now know as the Hope.

The rest of the great French Blue is thought to be represented in the 13.75 carat Brunswick Blue I and the 6.50 carat Brunswick Blue II, both named after Charles II, Duke of Brunswick, the 19th century's greatest collector of colored diamonds; when he died in 1873 he bequeathed his entire gem collection, including hundreds of colored diamonds to the city of Geneva. The next year the city auctioned off most of the collection, including the Brunswick Blues. These have been lost to history but doubtless survive as recuts still being traded today.13

Henry Philip Hope died in 1831. In 1901, Henry Francis Hope, the third heir to the diamond, whose gambling debts took him to bankruptcy, sold the stone to New York dealer, Simon Frankel for 33,000 pounds. Frankel sold the stone to dealer Salomon Habit who probably sold it to the Sultan of Turkey Abd al-Hammid II, an avid gem collector and excessively brutal ruler who was overthrown in 1909. The stone was sold privately to a dealer named Rosenau who sold it to Pierre Cartier of Paris in 1911. A year later Cartier patron Evalyn Walsh McLean, whose family owned the Washington Post, bought the stone for $180,000. Her life was marked by tragedy including the death in an auto crash of her nine year old son, divorce from an alcoholic husband(who later died in a mental hospital) and the suicide of her daughter at age 25 in1946. She died in 1947. Famous jeweler, Harry Winston bought her entire jewelry estate in 1949 for $1.5 million dollars. He kept the Hope nearly 10 years, then presented it to the Smithsonian Institution. On Nov. 8, 1958, the Smithsonian received a small package by parcel post bearing $2.44 in postage stamps and insured for $151.00. It contained the Hope.

II. The Corundum Gems

The corundum gems, ruby and sapphire, are the rare crystalline form of aluminum oxide, the second most plentiful compound in the earth's crust. When corundum is red, it is ruby; when any other color, or colorless, it is sapphire. [The purest corundum is colorless; the same is true for quartz, topaz, beryl, diamond, and many other gem materials; however except for diamond, colorless gems are not valued highly.] The fine red of rubies is due to a trace of chromium; the blue in sapphires comes from titanium and iron together; iron alone produces yellow. Various other elements color sapphires pink, peach, orange, green, lavender and purple. It must be said that the greens are not particularly attractive, being mostly dull olive green. Another point to keep in mind is that near red stones, either pinkish red or orange-red are sapphires, not rubies. A slight purplish tone is allowed in rubies, but pure reds have the highest value. Rubies are more expensive than sapphires because gem ruby crystals are generally much smaller than gem sapphire crystals, or a large crystal will have only a few small portions of gem quality material. Natural rubies over 3 carats are rare, and over 50 carats unheard of. In contrast, gem sapphire crystals up to 4000 carats have been found, and cut stones exist in the hundreds of carats at least for the blue and yellow.2, 3, 8

Rubies in the 1-3 carat range sell for $1000 per carat in commercial grades to $10,000 per carat for the finest quality, but larger stones are more expensive than diamonds. Recently the 15.97 carat Mogok Ruby sold for $3,600,000 or about $225,000 per carat.8

In contrast, synthetic ruby, identical in chemistry and characteristics, sells for as little as one dollar per carat for industrial uses, class rings, birthstone jewelry, etc. August Verneiul in France developed the flame fusion process in 1891-92 and marketed his rubies in 1902, creating a sensation and depressing the price of natural rubies for years. Flux-grown synthetics, developed by the Chatham brothers in San Francisco in 1978, are superior rubies used only for gemstones that sell for several hundred dollars a carat, still only a fraction of the price of the natural ruby.8 Imitation rubies or simulants have been around a very long time. Pliny, in first century Rome, might be called the world's first gemologist. In his monumental Natural History, he noted that "carbunculi are imitated by glass and such imitations at first sight are excellent. False carbunculi are detected by the lack of hardness of their powder and by their weight; further, one sees in false carbunculi certain small inclusions that is blisters and vesicles which look like silver".

Sapphires range in price from $50/carat for light blues with inclusions to $2000/carat for fine blues, hot pinks, peach-colored padparadshas or fine star stones. Much sapphire is heat treated to improve the color, usually light blue or greenish blue or gray to a better blue. Very dark blue, nearly black, sapphires so common in American jewelry stores in recent years are not particularly valuable.

III. Spinel

I will discuss spinel next since it is quite similar to corundum. Spinels display many colors, red, red-orange, pink, blue, violet and purple. True red is called 'ruby spinel'. At a Moh's hardness of 8, these magnesium aluminate stones are behind only diamond, corundum, and chrysoberyl. Refractive index is only slightly lower than the corundum stones. They are similar enough that many of the famous rubies of history, such as the Black Prince's Ruby and the Timur Ruby in the English Crown Jewels are actually spinels. The confusion between ruby and spinel need not have occurred. In the 10th century Arab scientist Al-Biruri listed very close to exact specific gravities for spinels, rubies and sapphires and separated them by names as well, 'balkhash' for red spinel and 'yaqut' for corundum. Like Arab medical knowledge, however, it did not cross over to most of Europe until the 17th and 18th centuries. In fact, the mineralogist, Rome de Lisle is credited with making the distinction in 1783.2 Because of its 'bridesmaid' status in multiple categories, spinel is priced much lower than ruby and sapphire, from about $75 a carat for pale lavender to $800 a carat for fine red. Synthetic spinel, known to many as the jewel in class rings, may also contribute to its undeserved lack of status.

IV. Chrysoberyl

Chrysoberyl, a beryllium aluminum oxide with traces of titanium and iron, is the crystal of three very different gemstones. With a hardness of 8 1/2 it is the third hardest of all the gems. In its commonest transparent form it is an underappreciated bright yellow to yellow-green gem. The name is from the Greek chrysos meaning golden.

Alexandrite, a darker form with chromium, was discovered in 1830 in the Ural mountains of Russia on the birthday of Czar Alexander II and the very day he came of age. It has a color change from green in daylight to red in candlelight or incandescent, the Romanoff imperial colors. Russian stones have the best color changes, but tend to be slightly cloudy and are rarely over 3 carats. Stones from Ceylon have a less spectacular color change, from brownish green to reddish mauve, but can be much larger. A recent find in Brazil has produced stones like Russian. 99% of the 'alexandrite' in jewelry is a man made simulant, vanadium doped corundum; it is violet blue in daylight and purplish red in incandescent light. Actual synthetic alexandrite from Russia has been marketed only in the past year. Natural alexandrites of fine quality are among the rarest and most expensive of gems, $3000-$10,000 per carat14 and are rarely seen.

Chrysoberyl catseye gems are also rare and expensive. Known in antiquity as oculis solis "eye of the sun", the gem's sharp ray of light on a ground of green to yellow to brown is a spectacular effect. It is due to thousands of fine parallel tubes. Several other gem species (tourmaline, diopside, beryl) may produce catseye effects, called chatoyancy. However, the term catseye without modifiers refers only to chrysoberyl. The gem gravels of Ceylon have been the most important source since ancient times.

V. Beryl

Crystals of beryl give us a variety of beautiful gems. Beryl is a beryllium aluminum silicate with a hardness of 7.5-8 and no tendency to cleave. When pure it is colorless and called goshenite after Goshen County, N.Y. With a trace of chromium and/or vanadium it becomes emerald. With iron it may be yellow or golden heliodor or green beryl or greenish blue to blue aquamarine. With manganese it becomes pink to peach colored morganite, or deep red beryl.

Nearly all fine emeralds still come from Colombia. Newer mines in Brazil and Rhodesia produce occasional fine stones. The oldest mine was Cleopatra's in Egypt which produced rather pale, cloudy stones. A small mine in the Alps at Habachtal, Austria has produced emeralds since Roman times. Nearly all emeralds of natural origin have inclusions called jardin, which may be solid, liquid or gas or all three. These and internal fractures make emeralds relatively fragile and heat sensitive. Special varieties of emerald include catseye and trapiche from the Spanish word for cartwheel. The later is cut as a cabochon showing 6 equal segments like a slice of orange due to layers of carbon in the hexagonal emerald crystal from one mine in Colombia.15 Catseye emerald can be very beautiful. A gem dealer friend of mine in Santa Barbara recently sold a 9 carat catseye emerald for well over a hundred thousand dollars.

Aquamarine crystals are far more common than emerald or morganite because iron is far more widely distributed than chromium or manganese. They also can be much larger, up to several hundred pounds and nearly flawless. There are natural fine blue aquamarines, but the great majority have been heat treated at 400 degrees C to convert the yellow and green form of iron to blue. Catseye aquamarines, mostly greenish, are produced occasionally. Aquamarine sells in the low hundreds of dollars per carat.

Morganite is named for the banker and financier, J. Pierpont Morgan, whose gem and mineral collections became the foundation of the American Museum of Natural History in New York. Like aquamarine, it comes mainly from Brazil and Madagascar. When a saturated peach color it is more valuable than aquamarine.

Red beryl is found in only one place in the world, the Wah Wah Mountains of Utah. Like morganite, it is colored by traces of manganese, but the color is far more saturated-a deep true red, sometimes with purplish overtones. It is called 'red emerald' by some dealers but this is an oxymoron. It is actually far rarer than emerald, and in recent years eye-clean one carat stones have sold for over $10,000 and half carat stones for $3000.15 Stones over one carat are rare, as large crystals are only 2 cm long and 1 cm wide and frequently have sandy cores.

VI. Topaz

To the ancients, topaz meant the gem we call peridot. In the 1700's a mine in Saxony produced yellow topaz as a royal enterprise and the name changes.12 This caused confusion with other yellow to orange stones such as citrine quartz which has been exploited by devious jewelers up to the present. Further confusion occurs because few people know that topaz comes in many other colors; pink, peach, raspberry, blue and sherry red. Imperial topaz orange to orange-red to purplish red sells for up to$1000 per carat. Like aquamarine, most of it has been heat treated to improve the color. Heat treatment is not considered to detract from the "natural" nature of these stones. Pink topaz was discovered in Russia during the 19th century. The gem was instantly so coveted that ownership was restricted to the czar and his family, hence 'imperial topaz'.14

In recent years blue topaz, mostly darker than the natural blue, produced by the irradiation of colorless topaz crystals, has become a popular and much less expensive substitute for aquamarine. Topaz is an aluminum fluosilicate with a hardness of 8. Unfortunately, it has an easy cleavage in one direction which may cause stones to be destroyed with a hard blow.

VII. Tourmaline

Tourmaline has a far more complex chemical formula than other gemstones. It is a borosilicate with numerous metals and semimetals substituting: Na, Ca, Mg, Fe, Al, and Li. In addition, manganese, copper and caesium may appear. The name comes from the Sinhalese 'turmali' via Dutch gem traders. Tourmaline has satisfactory hardness at 7 1/4-7 1/2 and no tendency to cleave. It has the largest color range of any gemstone. Tourmaline crystals are richly colored, often with two or more colors in a single crystal and often very lustrous and transparent, hence they are favorites of mineral collectors. The best gemstones come from Brazil, several countries in Africa including Madagascar and most recently Afghanistan. In the past, Russia, Burma, Ceylon, the state of Maine, and San Diego County have produced superb tourmalines, with the Maine greens and California hot pinks especially notable. At the turn of the century nearly all the large pink crystals of California went to the dowager empress of China for carving. In 1972, an exceptional pocket was found in the recently reopened Queen mine near Pala, California. This produced the famous 'blue caps' considered by many to be the finest matrix tourmaline specimens ever mined anywhere. Two of the best are in the Smithsonian and American Museum of Natural History. By strange coincidence, 1972 was also the year that a fine pocket was found in the old Dunton Gem Pit near Newry. Maine, after decades of minimal production. Interestingly and like the first diamond finds in Africa, tourmaline was first found in Maine not by miners or geologists, but by two school boys, Elijah Hamlin and Ezekiel Holms in 1820.12

VIII. Garnet

The word garnet comes from the Latin word for pomegranate, and most people think of garnet as a red stone, but it occurs in every color except blue, and the most valuable garnets are green.

Garnet is actually a group of closely related silicates with varying proportions of calcium, iron, magnesium, manganese and aluminum. All form dodecahedral crystals which can be very beautiful. All have a hardness of 7- 7 1/2 except demantoid which is 6 1/2. Pyrope garnets are deep red and best known as the tiny garnets in Bohemian jewelry. Almandine is deep purplish red. A mix of the two creates beautiful rhodolite, a lavender rose color. The green form of andradite is colored by chromium and called demantoid, or diamond-like, because it has high dispersion giving it fire. Most are very small but still expensive. Grossular garnet gives us yellow-orange hessonite or 'cinnamon stone' and light to deep green tsavorite, discovered in Africa in 1971, which has been a popular though expensive emerald substitute in recent years. Spessartine is a brilliant orange to orange-red and some of the best has come from the Little Three Mine near Ramona, California.

While common red garnets sell for as little as 5 to 15 dollars a carat, spessartines start at $100 per carat for small size, rising to $1000 per carat for a 10 carat stone.15 Green garnets command even higher prices-demantoid, $2000/carat for 1 to 2 carat stones and tsavorite $500-$2000 per carat.14

IX. Opal

Louis Leakey, the famous anthropologist, uncovered the earliest known opal artifacts in a cave in Kenya. Dating to about 4000 BC, they most likely came from Ethiopia.

In 50 BC, the Roman senator, Nonius had a brilliant hazelnut sized opal in a ring; according to Pliny, the great historian, Mark Anthony coveted it, possibly for his paramour, Cleopatra, and made Nonius an offer which was refused. Stern orders followed and Nonius fled for his life, banished from Rome forever.

Pliny, who died in 79AD, was the first gemologist in the opinion of many modern gemologists. He described opal as second in value to emeralds and having " the fire of the carbuncle (ruby or garnet), the glorious purple of amethyst, sea green of emerald, and all those colors mixed in an incredible way."

Early opals came from Hungary, from a mine which operated for two thousand years until 1922. These were white opals. The first black opal was found in Australia in 1901, at Lighting Ridge, although white opal had been mined for several decades at White Cliffs, hundreds of miles away. Taken to London, the blacks were dismissed as worthless or thought to be fakes!10 As their great beauty and true origin became known, blacks
soon surpassed whites in value. Today single black opals can command over $500,000, smaller fine stones, $8000-$12,000 per carat.15 Americans rarely see fine opal since our market won't pay over $4000 per carat. Of 100 black opals, a miner and dealer of long standing quoted in Fred Ward's 1997 book on opal estimated that 90 went to Japan,8 to the rest of Asia and only 2 to the U.S.A.10 Lightning Ridge remains the worlds sole source of true black opal.15 White opal is much more common and less expensive; most comes from Australia and Brazil.

In recent years, boulder opal has become popular and much more expensive. Although only a thin layer on ironstone, it is much more durable than solid opal, does not craze (develop fine cracks), yet has an appearance very similar to solid black opal, all at a fraction of the price, usually a few hundred dollars though connoisseur specimens command $5000 to $50,00015

Crystal opal is transparent with flashes of fire suspended in a colorless, yellow, orange,3 or blackish15 body color. 'Fire opal', from Mexico, is a variety of crystal opal with bright orange body color and may have no play-of-color at all; it is also seen as a brilliant orange faceted stone, beautiful but soft. Note that the term 'fire opal' refers to body color, not the play of color.3 Colorless or black crystal opals from Australia command $1000to $4000 per carat wholesale.15

The cause of the spectral colors of opal was not known until the 1960's, when electron microscopy revealed quite regular rows and lattices of silica spheres of identical size in a silica solution acting as a diffraction grating; small spheres give blue, large ones red. Opal was first synthesized by Pierre Gilson in France in 1974. In 1980 a Japanese firm introduced its synthetics and later another Japanese firm bought Gilson's process and name. Now the two Japanese firms compete for the relatively small synthetic opal market.15 A low power microscope can identify most synthetic opal.

X. Quartz Gemstones

Quartz, silicon oxide is the most common mineral on the planet. It is no surprise that quartz gemstones are abundant and diverse. Because it is not rare, at least since the enormous finds in South America a hundred years ago, even fine amethyst sells for only 30-50 dollars a carat. It can be extremely beautiful with red flashes from African or Uruguayan material, blue from Brazil. Citrine, which is rare in nature, is produced by heating amethyst. Golden-yellow is now preferred over the older orange-brown 'madeira' citrine. Ametrine, a mixture of citrine and amethyst, is found only in one mine in Bolivia. Colorless quartz or rock crystal is rarely seen as a cut gem but has been used in carvings and art objects since ancient times. Quartz with inclusions of golden rutile can be very beautiful and is often used today as one-of-a-kind jewelry. Recently composite stones of rutilated quartz backed with black onyx or blue lapis have come on the market and are an instant success.

Many other quartz gems are varieties of cryptocrystalline quartz, or chalcedony, microscopic crystals in massive form. Green chryoprase stained with nickel can substitute for jade, and chysocolla quartz, stained blue-green by that copper mineral, is like a translucent and much harder turquoise. Carnelian, stained reddish brown with iron, has been a gem for millennia. The bands of agate and patterns of jasper have infinite variety, even producing landscape scenes. Fire agate is like a super hard brown opal; the color is due to internal nodular layers coated with limonite. Black onyx is the most useful black material in jewelry. It is not as tough as black jade but takes a higher polish. The common 'Mexican onyx' is actually calcite-colorful but much softer and vulnerable to acid; those bookends, vases, desk sets, lamps and horses are not onyx.

XI. Pearl

Pearls have been equated with wisdom and purity since ancient times in all three of the major monotheistic religions, Christianity, Islam and Judaism. In Islamic mysticism, God's first creation was a huge tablet on which to record all of mankind's history and a sphere 70,000 leagues in size which became the ocean from which all life emerged. Both the tablet and sphere were made of pearl.14 To this day, cultured pearls which first appeared in the 1920's are rejected as somewhat blasphemous, as man playing God, in many Muslim countries. Pliny the Second wrote in the first century AD that pearls were the most valuable things known. Pearls worn by Cleopatra at a banquet for Marc Anthony were valued at 1.9 million ounces of silver. They retained high value and were prominent in royal regalia for two thousand years, but cultured pearls and the Great Depression caused the market to crash in 1930 and only in the last few years has it recovered.15 Now a necklace of 12-16 mm South Sea cultured pearls costs $25,000 to $75,000, and even a single 14 mm pearl $1200 to $1500.15

For over 2000 years the Persian Gulf supplied nearly all the oriental pearls. The loss of this source due to the oil industry and pollution since the 1950's means that today the only source of oriental pearls is estate jewelry. However, cultured pearls are widely accepted and the shift from Japan to the South Seas has provided more variety-pinks from Australia and Indonesia, cream from the Philippines, blue-gray from Malaysia, black from Tahiti. In addition we have lustrous mabe or blister pearls giving larger size for less money, irregular baroque natural pearls called 'keshi' from the South Seas and economical freshwater ones from China and our own country.

XII. Benitoite

In 1984, benitoite was named the state gemstone of California. It is a barium titanium silicate. It was discovered in 1906, and the source in the mountains of San Benito County remains the only meaningful occurrence in the world and the only source for gem material. 2, 3, 15

Benitoite is unique in several other ways as well. It is the only gem known in its crystal class. Its beautiful triangular crystals were predicted mathematically before any material in that class was ever found. The cut stones are brilliant blue, from colorless to deep blue and full of fire, since dispersion is only slightly less,15 equal to4, or slightly higher2,3 than diamond. In recent years a few pink stones have been faceted. Hardness is satisfactory at 6.5, but it requires some care in setting and wearing it. Stone sizes are small, as only tips of crystals are gemmy. Gems much over one carat are uncommon and only about five a year are over two carats.15 The largest documented stone is 7.8 carats and resides at the Smithsonian. Benitoites sell for over $1000 per carat15 and the price has been raising rapidly as the deposit has been largely worked out and available gems sold.3 To quote Joel Arem, Ph.D., author of the large Color Encyclopedia of Gemstones; "Benitoite is one of the most beautiful of all the rare gems, with the color of fine sapphire and the dispersion of diamond! Benitoite is one of the most desirable, beautiful and scarce of all gemstones"

XIII. Other Gemstones

There are many other beautiful gems worthy of discussion, but time and length constraints allow only a few comments.

Peridot, the August birthstone, sometimes known as the evening emerald with its soft, grass-green colors has been used since ancient times. The ancient mine on St. John's Island in the Red Sea supplied Cleopatra and produced until 1958. Burma has supplied larger stones, but they are not as clear. Arizona stones are clear but small and light colored. A recent find in Pakistan may solve all those problems. Peridot has a hardness of 6.5. Small sizes are inexpensive but large sizes can reach $200 a carat.

Tanzanite was discovered in Tanzania in the 1960's and named by Tiffany which was the first concern to market it. Tanzania remains the only source. It is a trichroic mineral, blue, violet, and red as the crystal transmits light in different directions. Most natural crystals are brownish and are heat treated to blue. Crystals can be cut to emphasize blue, purple or both colors; very rare strongly trichroic crystals have been cut, for collectors, only to bronze red stones.20 Hardness is 6.5 and most stones sell for $300-$900 a carat.14 A green variety colored by chromium and/or vanadium was discovered in 199220 and sells for up to $1800 a carat.15

Natural zircon crystals are reddish brown octahedrons which could be mistaken for diamond crystals. Heat treatment produces the colorless and sky-blue stones most commonly seen, and the fire of zircon's high dispersion is best seen in these. Cut zircons can be found in yellow, orange, green, red and lavender as well. Durability was discussed earlier. Prices are usually under $100/carat.

Kunzite is a variety of spodumene valued for its unique lilac pink color. It was discovered at Pala, San Diego County, California in 1903 and named for George Kunz, gemologist for Louis Comfort Tiffany, who first described it. Hardness is 7-7.5 but like topaz it has a perfect cleavage. It is relatively inexpensive since large gemmy crystals are not uncommon; Brazil and Afghanistan are major sources.

Moonstones are a variety of feldspar. Their optical effect adularescence, is due to fine internal layering. The beautiful blue sheen moonstone source in Ceylon is no more, but a new source in India producing 'rainbow' moonstone in many colors has helped fill the gap.

Iolite is another old gem which has inspired renewed interest as a sapphire substitute. It has been called 'water sapphire', and is a trichroic material showing violet and champagne as well as blue; these colors may appear with blue in a cut stone producing interesting effects. Iolite is a silicate with a hardness of 7-7.5 and is found in many parts of the world; small stones are inexpensive but clean stones of over 15 carats are worthy of museum display.3

I would love to discuss jade at length but that could be the source of an entire book, let alone a paper. Perhaps next time.


The lapis lazuli in Afghanistan are the oldest mines in the world. They have been producing for seven thousand years, from archeological evidence of trade routes.2 Egyptian tombs have yielded objects designed in gold and lapis dating from the Twelfth Dynasty, 24 centuries BC; The lapis came from Badakshan in ancient Medea, now Afghanistan.

The oldest book in the world, 4500 years old, the Papyrus Prisse in the Natural Library in Paris, has the statement: “But good words are more difficult to find than the emerald, for it is by slaves that it is discovered among the rocks.” The emerald mines in Jebel Zabarah, Upper Egypt were discovered in the early 1800’s yielding artifacts from about 1650 BC and a few low quality emeralds.2 Thus these mines had been worked for a thousand years before 1650 BC.

A necklace of graduated amber beads was found in a burial mound near Stonehenge dating from 2000 BC.2 By 1500 BC ornaments made from Baltic Sea amber were included in the royal tombs of Mycenae in Greece.

In the collection of Edward Gubelin, a necklace of emerald crystals and amethyst beads reportedly found in Pharaoh Tutankhamen’s tomb is illustrated in Peter Bancroft’s book.16 Cleopatra’s mines at Zabara and Sikeit in the Eastern Desert about 50 km inland from the Red Sea were visited by Peter Bancroft and Edward Gubelin in 1980. Stone structures had survived but most mine entrances were caved in and only two tiny emeralds were found in the dumps.16


The ancients taught that red stones (carnelian, ruby, garnet, and spinel) were good for bleeding and inflammation. Green stones were reserved for eye diseases, amethyst prevented intoxucation, sapphire cured boils, malachite was used as a local anaesthetic, but amber had the most universal application. Pliny ascribed to amber the ability to cure fevers, blindness, and deafness. Camillus Leonardus in his Speculum Lapidum of 1502 wrote that “amber naturally restrains the flux of the belly; it is an efficacious remedy for all disorders of the throat. It is good against poison. If laid on the breast of a wife when she is asleep, it makes her confess all her evil deeds. It fastens teeth that are loosened, and by the smoke of it poisonous insects are driven away.”2

Diamond dust was thought to be an effective poison in the 1500’s, in India, in Turkey (Sultan Bejazet II died in 1512 when his son Selim mixed diamond dust in his food) and in Italy (by Benvento Cellini 1500-1571). In 1613, the Countess of Essex poisoned Sir Thomas Overbury, who was imprisoned in the Tower of London, with mercury and diamond dust.


1. Sinkankas, John; Gemstone and Mineral Data Book
New York: Winchester Press, 1972

2. Desautels, Paul E.; The Gem Kingdom
New York: Random House, Ridge Press, ca 1979

3. Arem, Joel E.; Color Encyclopedia of Gemstones
New York: Van Nostrand Reinhold, 1977

4. Rutland, E.H.; An Introduction to the World’s Gemstones
Feltham, Middlesex, England: The Hamlyn Publishing Group, 1974

5. Bruton, Eric; Legendary Gems or Gems that Made History
Radnor, PA.: Chilton Book Co., 1986

6. Legrand, Jacques: Diamonds, Myth, Magic, and Reality
New York: Crown Publishers, 1980

7. Ward, Fred; Diamonds
Bethesda, MD: Gem Book Publishers 1993

8. Ward, Fred; Rubies and Sapphires
Bethesda, MD: Gem Book Publishers 1992

9. Ward, Fred; Emeralds
Bethesda, MD: Gem Book Publishers 1993

10. Ward, Fred; Opals
Bethesda, MD: Gem Book Publishers 1997

11. Ward, Fred; Jade
Bethesda, MD: Gem Book Publishing 1996

12. Sanborn, William B.; Tourmaline-The Mineral With Charisma
Gems and Minerals, Nov. 1976. No. 469 pp17-28, 94

13. Harris, Harvey; Fancy Colored Diamonds
Liechtenstein: Fancold Registered Trust 1994

14. Federman, David; Gem Profile - The First 60
Lincolnshire, IL.: Vance Publishing Corp. 1988

15. Federman, David; Gem Profile/2 The Second 60
Lincolnshire IL: Vance Publishing Corp. 1992

16. Bancroft, Peter; Gem and Crystal Treasurers
Tucsson, AZ: The Mineralogical Record& Sundance Press 1984

17. Schumann, Walter; Gemstones of the World
New, York, NY: Sterling Publishing Co. 1997

18. Bauer, Max; Precious Stones, Volumes 1&2
New York, NY: Dover Publications 1968 (original 1904)

19. Kunz, George Frederick; The Curious Lore of Precious Stones
New York, NY: Dover Publications 1971 (orig. Lippincott 1913)

20. Dirlan, Dona M. et al; Gem Wealth of Tanzania
Gems and Gemology vol. 28 Summer 1992 pp92-95

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