Chrome Diopside, Jet, Benitoite, Aquamarine, Rock Crystal Quartz, Red Beryl, Coral, Ivory, Danburite

Chrome DiopsideI was prompted to write these comments on chrome diopside after seeing a television shopping network's recent promotion of this gem as "Russian diopside" and their featuring it extensively in rings. Chrome diopside is a rich, emerald green variety of the mineral diopside which derives its color from chromium. A recent Russian find in 1988 is the source of the Tsavorite-like stones that are gaining in popularity and recognition today.As beautiful as the material is, its use in rings is risky at best. A hardness of (5.5-6), moderate brittleness, and cleavability limit its use to pendants, brooches and earrings unless placed in highly protective settings and given gentle treatment. For these other uses, though, the stone is beautiful and under-appreciated. Good cutting is important as this variety, especially in larger sizes, can be very dark. A good cut with fairly shallow angles can improve brilliance. Cabochons can be distinctive and attractive, and collectors eagerly look for the rare cat'seye form.A well cut piece of chrome diopside is a beautiful sight to behold, and a reasonably priced alternative to Tsavorite or chrome tourmaline.

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INCLUDEPICTURE "http://www.bwsmigel.info/gem.essayJPGs/CD-2849B.jpg" \* MERGEFORMATINET [Chrome diopside gems: emerald step cut, pear shaped cabochons, cat'seye set, pair of heart shaped brilliant cuts]ValueThe prime value factor for this gem is color, with medium dark green stones at the top. Such a stone in a larger size (2 cts or more) is especially rare since so many larger pieces suffer from light extinction and are too dark. Cat'seye stones bring a premium price. Fine cutting enhances value considerably by adding scintillation and brilliance.Gemological DataMakeup: a calcium, magnesium silicateLuster: VitreousHardness: 5.5-6Crystal structure: MonoclinicFracture: conchoidal to unevenCleavage: perfect in two directionsDensity: 3.29RI: 1.66 - 1.72Birefringence: .029

All text and images are Copyright of Barbara W. Smigel, 2012 unless otherwise indicated.No reproduction allowed without explicit permission.

JetIf you were to visit some of the many English websites devoted to this gem you would begin to realize, first, what a long history of use the gem has in the British Isles, and in the World, and second, how passionately some individuals feel about this lesser known gemstone.Jet, an opaque black, organic gem is usually described as a form of fossilized wood, but not in the sense of "petrified" wood, where the orginal cellular structure has been replaced by minerals and preserved. Jet is essentially a form of lignite coal, having its origin in buried wood from ancient forests, but much modified over millions of years by compression and heating deep underground. Occasionally you find the term "black amber" applied to jet, but that name is neither geologically nor gemologically accurate and must be considered a misnomer. Perhaps the name arose due to the fact that, like amber, jet will develop a static electrical charge when rubbed.One of the earliest of mankind's ornaments, jet beads have been unearthed from burial sites dating to the Bronze Age. The extension of the Roman Empire into the British Isles resulted in this black gem's use in the jewelry and art objects of rich Romans. Besides ornamental use, there are written records showing that powdered jet was used as a medication by the physicians of the 17th Century.The height of jet popularity was during the Victorian era. Upon her widowhood, Queen Victoria began wearing "mourning jewelry", primarily of jet, and continued to do so throughout her long life. The public emulated their Monarch, so that earrings, brooches and pendants were produced in large quantities and varying qualities and worn by everyone who could afford them. By the 1870s the gem had reached its peak of use and, until quite recently, has been in a consistent decline in its popularity ever since. Some speculate that the gem's association with death, mourning and sadness is responsible.Recently, signs of renewed popularity have been seen, perhaps as part of the general revival of interest in Victorian jewelry, or maybe due to its credentials as a gem with "metaphysical" attritubes and uses.

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INCLUDEPICTURE "http://www.bwsmigel.info/gem.essayJPGs/jet.earrings.jpg" \* MERGEFORMATINET [ Victorian jet jewelry: carved bracelet, bead necklace, earrings]Although there are known deposits of jet in many parts of the world, such as the USA (Utah, Colorado, New Mexico), Spain and the Middle East, historically, the premier site is along the Yorkshire coast, near the town of Whitby in England. Deposits there occur in shale beds which form cliffs along the beach and which extend under the sea. During the height of its popularity it was mined, but both before and after that period, a sufficient supply is picked from "land slides" and collected from material washed up on the beaches.Jet is soft (hardness ranging from 2.5 to 4) and somewhat brittle. Jet jewelry shouldn't be cleaned in an ultrasonic or with steam. It can be washed with warm soapy water and a soft brush, and a small amount of mineral oil applied to the surface will revive the shine.Simulants such as bog oak, "French Jet" glass, ebony wood, dyed horn, early and modern plastics and a rubber-like material called "vulcanite" are seen in the marketplace. One sure way to verify natural jet is to touch an inconpicuous part of the piece with a red hot needle and smell the results -- only jet will smell like burning coal.Value FactorsEven the best quality jet is modestly priced as a raw material. Most of the value of jet is associated with the artistry of carving or the historical context of the jewelry or ornamental piece. The finest pieces have a smooth, well polished surface that is free of cracks and blemishes.Gemological Properties:Chemical Composition: a mix of hydrocarbonsCrystal System: AmorphousRI: 1.64 - 1.68Density: 1.32Fluorescence: noneLuster: resinous to vitreousHardness: 2.5 - 4Fracture: conchoidalToughness: poor

All text and images are Copyright of Barbara W. Smigel, 2012 unless otherwise indicated.No reproduction allowed without explicit permission.

BenitoiteBenitoite is the quintessential American gemstone. Gem quality specimens are mined nowhere in the world except in San Benito County, California. Adopted as the California State gemstone, it is a favorite with collectors who admire its beautiful blue body color and its dispersion (.044) equal to diamond.Dispersion has thepotentialto cause stones to twinkle with flashes of red and green, although there is a trade-off between dispersion and body color. Some admirers are willing to forgo the dispersive display to get a darker blue stone, while others admire a lighter stone in which dispersion is more evident. The stone below shows a balance between visible dispersion and rich blue body color.

[A 2.0 carat stone showing dispersion]At hardness 6.5 it is tough enough for most jewelry applications. Its scarcity, however, makes it virtually unknown to the general public. The flattened triangular crystals are usually small and highly dichroic showing blue and colorless. Obtaining the blue color usually means orienting the crystal for lesser yield. Finished gems are almost always under 1 carat and usually less than .5 carat. No treatments or enhancements are known for Benitoite. It is truly one of the most beautiful (and wearable) of the collector gems.

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INCLUDEPICTURE "http://www.bwsmigel.info/gem.essayJPGs/BN-1262B.jpg" \* MERGEFORMATINET [Benitoite gems: varying in hue, tone, and clarity]ValueThis gem is quite expensive, especially for rich blue, clean stones at carat and above sizes. Clarity enhances value, especially in stones eyeclean or better. Very light and very dark stones are on the lower end of the value spectrum with medium dark stones at the pinnacle. Perfection of cut is sometimes sacrified, even by the custom cutter, to achieve the largest possible gem so windows and less than optimal proportions are fairly common.Gemological DataMakeup: a barium, titanium silicateLuster: VitreousHardness: 6.5Crystal structure: HexagonalFracture: conchoidalDensity: 3.67RI: 1.76-1.80Birefringence: .047

All text and images are Copyright of Barbara W. Smigel, 2012 unless otherwise indicated.No reproduction allowed without explicit permission.

AquamarineBlue to blue-green beryl, known as aquamarine, is quite a familiar stone, a staple in jewelry stores, catalogs and on home shopping programs, and rightly so. It is a magnificent gem which can be stunningly beautiful when well cut and polished and of good size and color. Unfortunately, huge amounts of material have been sold which either lack enough color to truly be called aquamarine or which are inferior in their fashioning. The most common natural color for this gem is a light to medium light slightly to moderately greenish blue. The name, aquamarine, then, indicates its resemblance to the color of sea water.Virtually all rough is heated to convert some of the green tones to blue. The treatment is undetectable and stable and therefore the consumer should assume all pieces to be heated unless otherwise specified. Recently a growing number of consumers have begun to appreciate the natural greenish gems.At hardness 7.5 it makes an acceptable ring stone and requires no special care or precautions in cleaning. The most common types of inclusions found in this variety are liquid filled fingerprints and hollow growth tubes. Major sources of stones include Brazil, Nigeria, Zambia and Madagascar. A common simulant for this gem is light blue synthetic spinel which can easily be distinguished from aqua by its optic character and refractive index. Aquamarine is the birthstone for March.

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INCLUDEPICTURE "http://www.bwsmigel.info/gem.essayJPGs/AQ-2699J.jpg" \* MERGEFORMATINET [Aquamarine gems: varying in color, quality and fashioning style]ValueThe deepest blue large stones have the highest value with medium and light blue stones of the same size fetching less. In smaller sizes, price still depends on color which is harder to obtain in small pieces. Blue-green stones of any size have traditionally had only about 50 -75% of the value of true blues, but this is changing as consumers are beginning to favor and seek out unenhanced stones. Mass production of blue topaz by irradiation in the 1980's briefly depressed the aqua market, but it rebounded when topaz took a nose-dive -- chiefly because the supply of darker blue topaz is virtually unlimited whereas only nature can make fine colored aquas which are now, and always have been, rare. Heating doesn't darken the color of aqua it just diminishes the green component. African aquamarine is relatively more abundant and can be less expensive that comparable Brazilian material.

Gemological Data:Makeup: a beryllium aluminum silicateLuster: vitreousHardness: 7.5Crystal structure: hexagonalFracture: conchoidalCleavage: noneDensity: 2.69RI: 1.57-1.58Dispersion:.014Birefringence: 0.006Pleiochroism: weak to moderate: blue and greenish blue in lighter or darker tones

All text and images are Copyright of Barbara W. Smigel, 2012 unless otherwise indicated.No reproduction allowed without explicit permission.

Rock Crystal QuartzI really had no thought of writing an essay about what I considered the least interesting of the crystalline quartz varieties: rock crystal. That is, until a friend gave me a gift of a beautiful "coffee table" book calledRock Crystal Treasures: From Antiquity to Today. The breathtaking pictures and well researched text served well, to give me a needed "attitude adjustment".The term, rock crystal, in use today, derives from the Greek word "krystallos" meaning - ice. In a treatise written around 300 BCE, Theophrastus (a pupil of Aristotle) explains the origin of rock crystal as being from ice that forms at such a high altitude, and therefore such a cold temperature that it was incapable of melting. This idea held sway until the 17th century when large deposits were located in Brazil, an obviously warm location. Today's major sources are Brazil and Madagascar with important secondary deposits in many other places including Arkansas and New York in the USA.

"Quartz Sceptre"

The Greeks were not the first appreciators of this gem, however. Babylonians circa 2000 BCE were advised that owning amulets or seals of rock crystal would increase a man's wealth and possessions. Making collections of rock crystal specimens with what were viewed as metaphysically important inclusions was a pasttime of the wealthy in ancient China. These items, purchased for purposes of contemplation and spiritual enlightenment, were sometimes gained at great price -- as there are records of rich men spending themselves into ruin to obtain the best pieces.Included quartzes also have a small share of today's commerce: with over 40 minerals known to occur as inclusions in quartz there are still plenty of specimens for the interested collector.

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INCLUDEPICTURE "http://www.bwsmigel.info/gem.essayJPGs/Q-240B.jpg" \* MERGEFORMATINET Rock crystal with inclusions of: tourmaline, pyrtie, edeniteRock crystal balls and skull carvings have long been given special significance in divination and necromancy. These artifacts have an enthusiastic audience in today's world, although cheap glass imitations abound. (By the way, the doubly refractive nature of quartz makes a dual image visible through them, not seen with glass). Early Christian art makes frequent use of rock crystal to symbolize purity, by its association with the Virgin Mary or angelic figures in paintings, tapestries and other art objects.Jewelers from earliest times until today have used rock crystal liberally. Some of the most well known and photographed examples include Edwardian, Art Noveau and Art Deco pieces in museum collections.In today's gem market, the place of rock crystal is a modest one. New facetors often choose it as an inexpensive, yet natural, practice material and carvers appreciate the availability of large, inclusion free pieces.

INCLUDEPICTURE "http://www.bwsmigel.info/gem.essayJPGs/Q-1686B.jpg" \* MERGEFORMATINET Carved rock crystalFor the last several decades colorless quartz has been made in laboratories for use in communications and electronic equipment. Although colored synthetic quartzes are something to worry about when purchasing amethysts or citrines, natural rock crystal still reigns for gem use, as it is cheaper and more abundant than the man made version.

Value FactorsAs huge crystals are available, the value of gems or carvings from this material is almost entirely due to the beauty, interest or artistry of the piece.

Gemological Properties:Chemical Composition: SiO2Crystal System: TrigonalRI: 1.54 - 1.55Density: 2.65Fluorescence: noneLuster: vitreousHardness: 7Fracture: conchoidalFluorescence: none

All text and images are Copyright of Barbara W. Smigel, 2012 unless otherwise indicated.No reproduction allowed without explicit permission.

Red BerylDiscovered in the late 1970's and still found in gem quality at only one site in the world, the Wah-Wah Mountains of Utah, red beryl, or Bixbite, is one of the world's rarest and most desirable gemstones. Typically as included as its fellow-beryl, emerald, few crystals approach gem quality. Most specimens of fine crystals are zealously guarded by mineral collectors and are never faceted.Found in white volcanic rhyolite; its color is contributed by cesium and manganese. Fewer than 10,000 stones are cut per year with more 95% of those being melee, mostly in lower grades. Various commercial mining ventures, in the past, have had sporadic success in producing stones, but a new enterprise, using more modern methods, is doing better. Red beryl remains, though, one of the most expensive of all colored gems. In recent years Russian synthetic red beryl has come on the market.

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INCLUDEPICTURE "http://www.bwsmigel.info/gem.essayJPGs/RB-255B.jpg" \* MERGEFORMATINET [Red beryl (Bixbite) gems: One of the rarest]Value FactorsThe great rarity of this material and its popularity with collectors means that almost any sized piece in any clarity and color grade can find a ready buyer. The best stones would have a raspberry pink to slightly purplish red color and be no more than slightly included. The rule of exponential increase with increase in size decidedly applies to this gem so often found in sub carat sizes. Cut is an afterthought, value-wise, in this material as cutters seek to produce the largest possible gem from their rough so windowed stones with poor proportions are in the majority.Gemological Data:Formula: Be3Al2Si6O18(+Mn, +Cs)Crystallography: HexagonalLuster: VitreousHardness: 7.5 - 8Cleavage: Indistinct.Fracture: conchoidal to unevenDensity: 2.66 - 2.70RI: 1.58 - 1.59

All text and images are Copyright of Barbara W. Smigel, 2012 unless otherwise indicated.No reproduction allowed without explicit permission.

CoralOther than shells and animal teeth, coral was one of the earliest jewelry materials enjoyed by our species. Neolithic amulets in red coral found in digs in Switzerland date back to 8000 BCE. Virtually every cilivization since then, which either lived in proximity to warm shallow seas, or had developed trade routes to such, has made enthusiastic use of this material.Living corals are tiny, colonial, filter-feeding invertebrates which manufacture solid living quarters out of calcium carbonate or protein. It is the collective, vacated homes of previous generations upon which the living coral film grows, and which we harvest and make use of in jewelry and carving.Historically the important gem corals have been divided into "calcareous" (stony) and "proteinaceous" (horny) types. At present, with these two traditional sources becoming scarce and demand, especially for inexpensive bead material driving the market, two other types ("sponge", and "bamboo" corals) are commonly seen.When someone describes a lipstick or a flower as "coral" colored, what comes to mind is a slightly orangey medium red. Traditionally this color, which occurs naturally in the calcareous corals, was the standard by which the group was judged. The globally wide-spread calcareous group is made up of species whose colors range from white, pink, and peach to "coral" red. The highly desired, hot, vivid reds come primarily from the Mediterranean and the seas around Japan, and for these specimens the competition is vigorous.They grow as branching structures which look something like a leafless tree, and in the rough, show minute parallel striations on their surface. Although rather soft by gem standards, they are reasonably tough and take a high polish. Natural colors are due to organic carotenoid pigments, but pieces of inferior color are sometimes dyed.

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INCLUDEPICTURE "http://www.bwsmigel.info/gem.essayJPGs/CO-3090B.jpg" \* MERGEFORMATINET [Calcareous corals: polished branch, 10x photo showing striations, top color red cabochon]

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INCLUDEPICTURE "http://www.bwsmigel.info/gem.essayJPGs/CO-4576J.1.jpg" \* MERGEFORMATINET [Calcareous corals: pink carving, white carving, baby pink beads]The other important group, whose houses are made of a tough, keratin-like protein called conchiolin or gorgonin, comprise the black and golden corals. Although not highly mineralized, the protein is very tough, so that properly prepared and polished pieces are near the equal of the stony types in durability and beauty, and sometimes exceed them in value. Colors range from black to dark brown to golden. The golden color is highly prized and can be natural, the result of injury or degeneration of the black coral organisms, or human-induced by bleaching with hydrogen peroxide. (After all, they are made of a hair-like protein).

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[Proteinaceous coral: polished golden coral branch]The blue and "sponge" corals are calcareous but with a much less compact structure than their pink and red relatives. As a result their texture is rough and porous and they take little, if any, polish. The natural colors are pinkish red with brownish areas, and grey blue, so they are usually dyed to improve their color, and/or resin impregnated to increase their durability.

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INCLUDEPICTURE "http://www.bwsmigel.info/gem.essayJPGs/resin.sponge.coral40x.small.jpg" \* MERGEFORMATINET [Enhanced red "sponge" coral bead, bead at 10x showing porous structure, at 40x showing resin in openings]

INCLUDEPICTURE "http://www.bwsmigel.info/gem.essayJPGs/Blue.coral.15x.small.jpg" \* MERGEFORMATINET [Enhanced blue coral beads, bead at 15x showing structure]Bamboo coral, or "sea bamboo" has an interesting structure that explains its name. The coral skeletons consist of stretches of branch-like, stony calcium carbonate material, interspersed with joint-like regions of gorgonin protein. The natural color is creamy white with brown or black. Sometimes the harder sections are cut out and dyed to make small beads or cabs, while in other cases larger pieces are used which incorporate both regions and retain the banded patterning.

[Natural bamboo coral branch, dyed bamboo coral beads]Like most other organic materials, fossilization of coral can occur through petrifaction or the creation of pseudomorphs. Fossil corals from ancient colonies which have become silicated, make durable (hardness = 7) and interesting cabochon materials.

[Fossil Coral from Indonesia]In addition to various enhancements, there are coral simulants in the market, such as, dyed shell, and lab creations such as "Gilson Coral" (although not a true synthetic, the composition, appearance and properties are quite close). Less convincing simulants, such as glass and plastic, abound in inexpensive costume jewelry.Coral gems with their hardness of 3 - 4 should be worn and cleaned gently. Warm water and mild detergent are best for cleaning needs, and daily wear rings or bracelets are risky. The calcareous types can be damaged by exposure to acids and the proteinaceous types should be protected from high heat and long exposure to water.Value FactorsBy far, the most valuable corals are the natural reds, blacks and golds. Fashions change in this regard, though, as the white and baby pinks were preferred in Victorian times. A good polish and freedom from blemishes is important and, of course, the artistry of the fashioning must be taken into account.Some locales from which corals are obtained have been over-fished or environmentally degraded, leading to protective management of the stocks and scarcity of supply. Happily, in the future it may be possible to "farm" some types of corals to supplement our needs. There are pilot programs attempting this in Japan and Hawaii.Gemological Data:Varies by species

All text and images are Copyright of Barbara W. Smigel, 2012 unless otherwise indicated.No reproduction allowed without explicit permission.

IvoryIvory, as defined by most gemologists, is derived from the teeth or tusks of mammals, although some other materials with similar characteristics and appearance have traditionally been given this name. Examples of tooth ivory are less common, and generally limited to: hippo and sperm whale teeth (teeth are defined as dentition which is not visible when the mouth is closed, whereas a tusk protrudes from the closed mouth). Tusks from African and Asian elephants, wild boars, walruses and narwhals as well as extinct mammoths and mastodons have been used throughout history (and pre-history) to produce a range of ornamental and useful objects. Simple ivory amulets and tools have been found in archeological sites dating 7000 years before present. The Chinese penchant for ivory goes far back in their history (5000 BCE) as does their supremacy in the art of carving it into intricate designs and inlays. By 500 BCE India was engaged in a vigorous ivory export trade.The properties of ivory vary somewhat by species in terms of hardness, uniformity and the basic shape of the raw material. Some sources, like elephant tusk, provide large, mostly solid pieces, whereas other types (like narwhal tusks) are mostly hollow, and others like hippo teeth are smaller, which can limit useage to certain sizes or shapes. The hardest and whitest ivory is derived from hippo teeth which makes them more difficult to carve, but less likely to stain and crack.ELEPHANT IVORYThe majority of very old ivory carvings and ornaments are probably from Asian elephants whose tusks are relatively smaller and found only on male animals. Within the last several hundred years, however, the African elephant has been the ivory provider of choice, due to its historically greater population numbers, larger tusks, and the fact that both sexes are tusked.The once thriving commerce in African elephant ivory would stagger today's conservation minded individual -- before plastics were invented in the late 19th century, ivory was the source for such diverse and universal items as buttons, hair combs, jewelry, furniture inlay, billiard balls and veneer for piano keys. (The finest billiard ball makers produced only three balls per tusk).By the 1970's when the environmental movement swept the Western world, the consequences of this carnage were obvious. In 1989 a world-wide ban on elephant ivory trade was instituted as part of CITES (Convention on the International Trade in Endangered Species). This treaty has had mixed, mostly positive, results, with elephant populations rebounding to a degree, and interest in still-legal forms of ivory and ivory simulants increasing. The down-side is the inevitable escalation of value of elephant ivory objects, and consequent stimulation of black market trade. Currently small parcels of CITES approved ivory from elephants dying of natural causes or captured goods from smugglers are legally sold to finance conservation efforts.

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INCLUDEPICTURE "http://www.bwsmigel.info/gem.essayJPGs/Leg.elep.scrim.jpg" \* MERGEFORMATINET [19th century Chinese dice cup and Victorian needle case, Victorian Era brooch, Contemporary legal elephant ivory scrimshaw pendant]"FOSSIL" ELEPHANT IVORYUntil about 7-10,000 years ago, mammoths ranged over Eurasia and mastodons over the Americas. Throughout their long reign as species, innumerable individuals died and were buried in mud, ice or peat. These artifacts, although not mineralized in the true sense of fossilization, have been preserved, and due to erosion, geological events or mining have been, and are being, unearthed and used as ivory sources.Like all elephant ivories these show distinct structural properties which result in a layered structure in longitudinal section and a cross hatched pattern in cross section. This characteristic called the "engine turned" effect is diagnostic of elephantine ivories and absent in all other forms. These ancient ivories sometimes have acquired unusual colors through long contact with minerals and mineral solutions.Such materials are not covered by CITES, indeed the species arealreadyextinct, and are becoming very popular. In the US, digging for anything on public lands is restricted by Federal land management agencies, but in Alaska, Canada, Greenland and Siberia, Inuits and other native peoples have been greatly benefited by the ability to harvest, fashion, and trade these items to an eager world market.

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INCLUDEPICTURE "http://www.bwsmigel.info/gem.essayJPGs/Mast.ivory.ojime.sm.jpg" \* MERGEFORMATINET [Contemporary mammoth ivory amulet, mammoth ivory showing "engine turned" effect, mastodon ivory ojime bead (19th century Japanese)]MARINE MAMMAL IVORYMarine mammals, particularly walruses, and toothed whales (sperm whales and orcas) have been a long treasured source of ivory for populations in locations where these species are common. Inuits, in fact have a much longer history of walrus ivory use than that of the much harder to kill whales. Marine mammals are protected from harvest, except for quotas for certain native peoples who have the right to use their legal catches for meat, hide, bone and ivory and the right to fashion and sell such artifacts. This represents a welcome economic benefit for such groups, as well as a valuable stimulus to preservation of ancestral arts and crafts.Walruses being at least semi-terrestrial animals have also been long buried and recently unearthed -- such "fossil" walrus ivory can also be legally collected and traded by indigenous peoples. In structure walrus ivory shows a distinct core region when sliced in cross section.

INCLUDEPICTURE "http://www.bwsmigel.info/gem.essayJPGs/WALRUS.TUSK.XS.jpg" \* MERGEFORMATINET [Contemporary legal walrus ivory bead, "fossil"walrus tusk slice showing mineral staining and central core]Sperm whale teeth have a long history of use in New England in the USA, and throughout the whaling nations of the world. The most common way the teeth were fashioned was by leaving them whole or taking small sections and decorating the piece with an engraved and colored design, called scrimshaw. Most often the designs were related to nautical or whaling subjects.

[Sperm whale tooth scrimshaw: Image courtesy of Booth Trading Company]OTHER IVORIESAt present hippos are not considered endangered and are not covered by CITES. They shed teeth naturally which people located in their habitats can collect and legally sell to much of the world (the US, UK and most European countries, however, do not allow any "raw" ivory to be imported, regardless of source). There is a huge market in Japan and China, though, where small carved objects of hippo ivory have largely replaced those of elephant ivory.

[Antique whole hippo tusk carving: Image courtesty of Dr. Terrill Smith, contemporary Japanese hippo ivory netsuke]During the Victorian Era many gems of organic origin were in favor, including obscure ivories such as seen in this circa 1870 brooch fashioned of two animal (pig?) teeth.

[Victorian animal tooth brooch]Although most would define ivory as deriving from mammal teeth, one notable exception is the case of hornbill "ivory". Technically the material is more akin to horn than tooth as it derives from the "casque" or second beak which grows on top of the regular beak in this group of souteastern Asian birds. It is a golden color and exceptionally translucent with the most coveted and expensive specimens showing a bright red "rim". These birds are endangered and cannot be legally hunted, nor can items from them be traded except under restricted conditions as certifed antiques in some parts of the world.

INCLUDEPICTURE "http://www.bwsmigel.info/gem.essayJPGs/hornbillnetsuke.jpg" \* MERGEFORMATINET [Kenyalang "Helmeted Hornbill": Image courtesy of Sarawktourism.com, antique hornbill ivory netsuke]IVORY SIMULANTS/ENHANCEMENTSWith the current restrictions on ivory trade in place, we can easily understand the emphasis on simulants in today's market, but simulation of ivory is nothing new. Ivory has always been an expensive, limited, and much imitated material. Two natural materials which have a long histories of use as substitutes, are bone and "vegetable ivory" derived from tagua (S. America) or doum palm (Africa) nuts. Early plastics such as celluloid and casein were widely popular as faux ivory from the late 19th century, with modern plastics carrying on the tradition today.Simulants can be detected relatively easily by microscopic examination. Plastics and vegetable ivory show a complete lack of the "structure" typical of ivories. Bone, although showing internal patterns that verify its origin as an animal tissue, is quite distinctive with its Haversian Canals.

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INCLUDEPICTURE "http://www.bwsmigel.info/gem.essayJPGs/Veg.ivory.sm.jpg" \* MERGEFORMATINET [Contemporary bone necklace, early 20th century celluloid brooch, contemporary tagua nut carving]Relatively little in the way of enhancement is used on ivory, the most common being the staining of newly carved items with tobacco juice, tea or other dyes to simulate the appearance of great age. Similar effects can be obtained with gentle heat or irradiation. Mild bleaching solutions of hydrogen peroxide or chlorine can even out color, and remove some blemishes, and is occasionally done. Very rarely specimens of bone or ivory are dyed blue with copper salts to simulate a rare, naturally colored, fossil ivory known as odontolite.CAREAs a soft organic gem, ivory deserves gentle cleaning and careful use. Wiping the piece with a damp cloth should suffice for most cleaning needs and prolonged exposure to high temperatures should be avoided.Value FactorsBecause important legal and ethical factors restrict and influence the market for ivory, it is difficult to generalize about value. Clearly, antique ivory objects, under conditions where they can be legally traded, are valued based on the rarity of the materials, their age, provenance, and the artistry of their fashioning. Examples of items for which collectors (ethical and otherwise) will pay dearly are large elephant ivory pieces, narwhal tusk work, and most precious of all, hornbill "ivory" carvings.In the arena of legally traded ivories and ivory simulants, most items are modestly priced with rarer and larger items and those with greater antiquity or higher artistic merit at the top, and vegetable ivory, bone, and plastic simulants in the lower brackets. "Fossil" ivories which have been stained attractive colors through natural mineral processes do bring a premium price. In any ivory piece, translucence and freedom from cracks is valued. Yellowish, orangey and brownish hues (unless they are deliberately applied to simulate age) add value as a patina.Gemological Properties(These vary somewhat with species, the ones below are for elephant ivory)Makeup: 65-70% hydroxyapatite Ca5(Po4)3OH, plus collagen and elastin protiensCrystal system: none, amorphousRefractive Index: 1.54Hardness: 2.5 - 2.75Toughness: fairSpecific Gravity: 1.70 - 2.0Cleavage: noneFracture: splinteryUV Reaction: fluoresces weakly to strongly bluish white to LW, less to SWLuster: greasy

All text and images are Copyright of Barbara W. Smigel, 2012 unless otherwise indicated.No reproduction allowed without explicit permission.

DanburiteFirst discovered in Danbury, Connecticut, in 1839, this gem has been found and mined in Japan, Russia, Mexico, Burma, and Madagascar. It ranges from milky translucent white, to transparent pieces of colorless, light yellow, tan, and rarely, very pale pink.The type locality of the US deposit which was named for the town nearby, has long since been covered over, and made inaccessible by the growth of this now rather large community. Pieces that actually originated from this location are now prized by collectors.Danburite is found in metamorphosed limestones and low temperature hydrothermal veins, but few its numerous locales yield either impressive crystals for the mineral collector, or transparent pieces of sufficient size to facet. Joel Arem in his "Color Encyclopedia of Gemstones" states that although the mineral itself is relatively common, large, facetable pieces are rare. The crystals often have a distinctive wedge-shaped habit and nicely terminated ones are beautiful to see. The best crystals, mostly translucent or milky white have historically come from mines in Central Mexico. Although similar in shape and color to topaz crystals, Danburite can be distinguished by its lack of cleavage compared to the strong cleavage seen in topaz.

[A fine, transparent, orthorhombic Danburite crystal, set with a pink sapphire and a brown diamond, in a silver and 18k gold necklace]Likewise, cut gems have a luster and refractive index very close to that of white, yellow and brown topaz, but gemologically these two species can be separated by the difference in specific gravity (topaz is denser) and birefringence, which is higher in topaz. The distinctive blue fluorescence of many Danburites when exposed to ultraviolet light, is also an indentification criterion.

[Sawn pieces of Danburite rough from Mexico, some of the crystal faces can be seen]Although it is not common enough to become amajorcommercial jewelry stone, thereisenough material for gem collectors, and adventurous jewelry lovers to bring this lovely and under appreciated gem into their collections. Danburite is also sought out by those who are interested in the metaphysical properties ascribed to gems and crystals.

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INCLUDEPICTURE "http://www.bwsmigel.info/gem.essayJPGSnew/DA-1650B.jpg" \* MERGEFORMATINET [Faceted Danburites from various locales, showing the brilliance and luster typical of well cut stones]With no cleavage, good toughness and a hardness of 7; Danburite makes an excellent jewelry stone, that surpasses quartz and beryl in brilliance. Its modest dispersion means that although very brilliant, cut gems lack "fire"(spectral color flecks). Due to some heat sensitivity (the heat from a jewelers torch will fuse it), it is best not to subject this gem to steam cleaning, but otherwise, it requires no special care, and can be used in all applications, including rings and bracelets. There are no known enhancements, synthetics or imitations on the market.Value FactorsThe tried and true value factors for gems in general apply to this species very well. All other things being equal, larger, cleaner, and better cut stones are worth more per carat. The only caveat here, might be that a noticeably pink stone (most as so pale as to be essentially colorless) would surpass the colorless, yellows, and browns in value. In my opinion, for a relatively rare, brilliant, and quite wearable gem, prices are low enough to represent a real gem bargain.

Gemological Properties:Makeup: Calcium Borosilicate: CaB2(SiO4)2Hardness: 7Birefringence: .006Dispersion: .016Toughness: goodCrystal System: OrthorhombicLuster: vitreousDensity: 3.00Pleochroism: noneRI: 1.63-1.64Cleavage: noneFluorescence: Frequently shows a strong light blue to blue green to LW UV and a weaker reaction to SW UV

All text and images are Copyright of Barbara W. Smigel, 2012 unless otherwise indicated.No reproduction allowed without explicit permission.