Index | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z C CABOCHON A cabochon is a stone that has a rounded, domed surface with no facets. A cabochon garnet is also called a carbuncle. CAIRNGORM Cairngorm is a yellow-brown type of smoky quartz that is often used in traditional Celtic jewelry. Cairngorm is not Scottish topaz. The supply of cairngorm is virtually exhausted, so heat-treated Brazilian amethyst is used as a substitute in Scottish jewelry. CALCITE Calcite (Calcium Carbonate, CaCO3) is a very common mineral that comes in a wide variety of forms, shapes and colors. The trigonal crystals range from translucent to transparent. Transparent calcite exhibits a double refraction effect (when you look through the crystal, single items are doubled). Calcite has a hardness of 3 (most forms), a specific gravity of about 2.7, a refractive index of 1.49 and 1.66, and a white streak. CALIBRE-CUT Calibre-cut stones are small stones that are cut into special shapes that are meant for use in commonly-used designs. These stones usually have step-cut facets and are generally rectangular shaped. CALIFORNIA RUBY A California ruby is actually a pyrope garnet (and not a ruby at all). CAMEO A cameo is a relief carving (a carving that comes up above the surface) on a shell or stone. In multi-colored cameos, a layered substrate is used (with two different colors), and when part of the upper layer is carved away, the second color emerges as the background. Cameos are frequently portraits of women. Many imitation cameos are made from pressed glass or plastic; some of these use two different colors, like the imitation cameo pictured above. CAMEO HABILLE A cameo habille (meaning "dressed cameo" in French) is a "jewel within a jewel," a cameo in which the subject carved in the cameo (usually a woman) is wearing a miniature piece of jewelry (like a tiny diamond necklace with a stone embedded in the cameo). CANARY DIAMOND Canary diamonds are diamonds that have a deep yellow color. Diamonds are precious, lustrous gemstones made of highly-compressed carbon; they are one of the hardest materials known. Diamonds have a hardness of 10, a specific gravity of 3.5, and a refractive index of 2.417 - 2.419 CAPE AMETHYST Cape amethyst is a form of amethyst that is layered or striped with milky quartz. Cape amethyst is a translucent gemstone that ranges from light- to medium-purple and has white bands. CARAT A measure of weight used for gemstones. Not to be confused with “karat”, which is a measure of gold alloy purity. Often abbreviated as “ct.” one carat is equal to 200 milligrams (one fifth of a gram). Gemstones are measured to the nearest hundredth carat (known as a “point’). A hundredth of a carat is called a point. For example, a .25 carat stone would be said to have twenty five points. A carat is one of the 4 Cs of diamond grading. The others being Clarity, Cut, and Color. The carat unit was introduced in 1907. CARBONADO A carbonardo is a rare type of opaque black diamond; they are not used for jewels, but for items like drilling bits and abrasive wheels. They were once thought to have been formed as a result of a comet impact 2 billion years ago, but this is no longer thought to be true. The largest diamond ever found was a carbonardo that weighed over half a kilogram. Carbonadoes are found in Bahia, Brazil, South America. Unlike other diamonds, carbonadoes are not found in a crystallized form - they are found in irregular or rounded fragments. Carbonadoes have a hardness of 10 and a specific gravity (density) of 3.1-3.3. Diamonds have a very hard polycrystalline carbon structure. CARBUNCLE A carbuncle is a cabochon garnet. CARNELIAN Carnelian (also called cornelian and carneole) is a reddish form of chalcedony (a type of quartz). This translucent stone has a waxy luster. The best carnelian is from India. Most commercial carnelian is really stained chalcedony. Carnelian has a hardness of 7 and a specific gravity of 2.61. CARTIER, LOUIS Grandson of Louis Francois Cartier, the founder of the House of Cartier in Paris—which fast became one of the world’s leading jewelry firms. Louis was responsible for popularizing the use of platinum in jewelry during the early 1900s. Famous for his garland designs during the Edwardian period, Louis Cartier also was influential during the Art Deco period, as well as the designer responsible for inventing the first wristwatch. CASTING Casting is the process in which metal is shaped by melting it and pouring it into a mold. This process has been used for thousands of years. Molds are made from many materials, including plaster compounds. Some different methods of casting include the lost wax process, centrifugal (or investment) casting, and sand casting. CATHEDRAL SETTING A cathedral ring setting is a simple band that arches when seen from the side (like the arches of a cathedral). CAT'S EYE CHRYSOBERYL Cat's eye (chatoyant chrysoberyl) is a yellow to green-yellow to gray-green stone with a bright, pupil-like slit that seems to move slightly as the stone is moved. Most Cat's eye is cut as cabochons to maximize the distinctive pupil-like effect. Most cat's eye chrysoberyl is found in Brazil. Cat's eye chrysoberyl has a hardness of 8.5. This stone is sometimes enhanced by irradiation (this process improves the color and accentuates the stone's asterism). CELTIC JEWELRY Celtic jewelry was made by the Celts in Ireland, Wales, Scotland, and Brittany. The Celts used bronze, silver and gold in their jewelry and stones like cairngorm and amethyst. Circular brooches with a long, hinged pin, called pen annular brooches, date from ancient times. The earliest-known piece of Celtic jewelry is the Hunterston brooch from 700 A.D. CENTER STONE The prominent precious gemstone which is the centerpiece of a ring setting. CFW CFW is an abbreviation for cultured freshwater pearls. CHALCEDONY Chalcedony is a family of minerals (microcrystalline quartz) that are often milky to gray to bluish in color. Chalcedony includes agate, carnelian (waxy red), chalcedony (blue), chrysoprase (green), onyx (black and white), bloodstone, sard (brownish-red), jasper (hornstone), seftonite, and others. Chalcedony is porous and translucent. Chalcedony has a hardness of 6.5-7 and a specific gravity of 2.6. CHAMPLEVE (meaning sunken enamel) Champleve (also called email champleve) is a method of applying enamel to metal in which the design is first outlined on the metal surface by cutting lines into the surface. The engraved grooves are then filled with enamel, then fired to a glassy sheen, and polished. Champleve is similar to cloisonne, but not as delicate. CHANDELIER EARRING An earring with a drop that dangles like a chandelier. CHANNEL SET Channel set jewels rest in a metal channel, held in only by a slight rim which runs along the edges of the channel. Channel set jewels are usually round or baguette shaped. CHANEL From her first millinery shop, opened in 1912, to the 1920s, Gabrielle 'Coco' Chanel rose to become one of the premier fashion designers in Paris, France. Replacing the corset with comfort and casual elegance, her fashion themes included simple suits and dresses, women's trousers, costume jewelry, perfume and textiles. CHARM A decorative pendant or trinket to be worn on a bracelet, necklace or earring. CHARM BRACELET A link bracelet to which charms can be attached. CHASING Chasing is a type of metal decoration in which the metal is manipulated using a hammer and a punch, resulting in an effect similar to engraving or embossing. CHATON A chaton is a stone with a reflective metal foil backing. CHATON SETTING A chaton setting (also called coronet or arcade setting) is one in which the stone is held in by many metal claws around a metal ring. CHATOYANCY Chatoyancy is the lustrous, cat's eye effect seen in some cabochon stones, like cat's eye, tiger's eye (pictured above), and sometimes in other stones, like aquamarine. In chatoyancy, light is reflected in thin bands within the stone. Chatoyant stones are cut in cabochon to maximize the lustrous effect. CHENIER Chenier is fine, hollow tubing that is used in the production of some jewelry findings (like clasps and joints), and lately, in the actual production of jewelry. The hollow tubes are lightweight and save in the use of gold. The tubes are hard to bend when they are empty, so a metal rod is inserted before bending, facilitating the bending. CHOKER A choker is a type of necklace that fits tightly around the neck. Chokers are from 14" to 16" in length. CHROME DIOPSIDE Chrome diopside is an emerald-green colored gemstone. It is a chromium-rich variety of the common mineral diopside (Calcium magnesium silicate). Chrome diopside has a hardness of 5 to 6 and a specific gravity of 3.3 to 3.6. CHROMIUM Chromium is a hard, shiny, gray-white metal. This metal resists corrosion very well and is used in costume jewelry as a coating over other metals. CHRYSOBERYL Chrysoberyl is a hard stone that ranges in color from yellow, to brown, to green. Some chrysoberyls include alexandrite and cat's eye. CHRYSOLITE Chrysolite is a name used for many stones. During Victorian and Edwardian time, it referred to green-yellow chrysoberyl. It can also refer to peridot. Long ago, the name was used to refer to almost any yellowish gem. CHRYSOPRASE Chrysoprase is the most valued variety of the mineral chalcedony (microcrystalline quartz) that contains nickel, giving it an apple-green color. Chrysoprase is porous and translucent. It is usually cut as a cabichon, and has been used since ancient times. Chrysoprase has a hardness of 7 and a specific gravity of 2.6. Chrysoprase is mined in Australia, Russia (the Ural Mtns.), Brazil, and the western USA. Chrysoprase is sometimes called "Australian jade," but it is not related to jade. Hard-to-detect imitation chrysoprase is made by staining agate with chromium salts. CIRE PERDU Cire perdu (French for "lost wax") is a process of casting metal in which the original model is sculpted in wax. The wax is entombed in clay, and the wax is then melted out, producing a hollow mold. The mold is then filled with molten metal. The clay is broken off and the cast metal remains. CITRINE Citrine (from the French for "lemon") is a rare, yellow type of quartz, a semi-precious stone that ranges in color from pale yellow to orange to golden brown. The best quality citrine is found in Brazil. Many of the stones sold as citrine are actually heat-treated amethysts. Citrine has a hardness of 7 and a specific gravity of 2.65. CLARITY Clarity is the clearness of a gemstone, or the lack of internal flaws. The clarity scale for diamonds runs from FL (flawless, with neither internal nor external flaws), to I3 (having many clearly visible imperfections using only the naked eye). A ten-power loupe is used to examine a diamond for clarity. CLASP A clasp is a fastener that can open and close, attaching two things together (for example, the two ends of a necklace, or a pin to a garment). The clasp on a piece of jewelry can tell you a lot about the piece, including giving an indication of its age (by determining when that particular type of clasp was invented and looling at the wear on the clasp), its quality (better quality pieces generally have better-quality clasps), and its composition and manufacturer (the clasp is often where the maker's stamps are). For example, the spring ring clasp was invented early in the 1900's; jewelry made prior to 1900 or so will not have a spring ring clasp. Some other common clasps include the lobster claw clasp, the box clasp, the barrel clasp, the fold-over clasp, the hook-and-eye clasp, and the bar and ring toggle clasp. CLAW A claw is a metal prong that holds a stone securely in a setting. CLAW SETTING A claw setting is one in which a series of metal prongs (called claws) holds a stone securely in a setting (the claws grips the stone just above the girdle of the stone), with no metal directly under the stone (it is an open setting). This setting lets light in under the stone, so this type of setting is usually used for transparent, faceted stones. The modern-day claw setting became popular in the 1800's. CLEAVAGE Cleavage is the natural in which way a mineral breaks, along certain planes based on its internal crystalline structure. CLOISONNE Cloisonne is a method of applying enamel to metal in which the design is first outlined on the metal surface using a metal wire. The space between the wires is filled with enamel and then fired to a glassy sheen. CLOSED SETTING A closed setting is one in which the back of the stone is not exposed (the metal is not cut away behind the stone). CLOUD A cloud is a type of inclusion in some gemstones that has a milky appearance (and greatly affects the value of the stone). A cloud is usually composed of a cluster of tiny inclusions. CLUSTER SETTING A cluster setting is one in which small stones or pearls are set around a larger stone. COLLET SETTING A collet setting is a very early method of setting gemstones. A collet is a thin, round band of metal that goes all around the stone. One edge of the metal is crimped over the edges of the stone and the other edge is soldered to the metal of the jewelry, holding the stone in place. This closed setting sometimes also had metal claws along the outside to hold the stone even more securely (the claws were not used much after the 1200's and 1300's. COLLARETTE A collarette (also known as a bib necklace) is a short necklace with flowing ornaments at the front. COMPOSITE SUITE A composite suite is a piece of jewelry that can be taken apart into two or more pieces which can also be worn. For example, a necklace may be disassembled into two bracelets. CONFETTI LUCITE Confetti lucite is transparent plastic with glitter or other small pieces of material within it. Whimsical bangles, earrings, pins, necklaces and other jewelry have been made from confetti lucite. CONQUISTADOR Usually used in reference to 16 th century Spanish soldiers who conquered the civilizations of Mexico, Central America, and Peru. COPPER Copper is a soft metal often used in jewelry. It is used in making bronze, brass, and gold alloys. The enameled copper leaf pin above is marked Matisse, from the "Renoir of California" jewelry company. CORAL Coral is an animal that grows in colonies in the ocean. Coral polyps secrete a strong calcium structure that is used in jewelry making. Coral ranges in color from pale pink (called angelskin coral) to orange to red to white to black. The most valued colors are deep red (called noble coral) and pink. In jewelry making, coral is either carved into beads, cameos, or other forms, or is left in its natural branch-like form and just polished. It used to be thought that coral protected the wearer, so it was a traditional gift to children. Coral has a hardness of about 3.5 and a specific gravity of 2.6 to 2.7. Since it is composed of calcium carbonate, coral will effervesce if touched with acid. Imitation coral is made from glass, porcelain, or plastic. CORONET SETTING A coronet setting (also called chaton or arcade setting) is one in which the stone is held in by many metal claws around a metal ring. CORUNDUM Corundum is a very hard mineral (hardness 9); only diamond is harder. Corundum is called ruby or sapphire, depending on the color (which depends on which metallic oxides are present). In its rare pure form, corundum is colorless and called white sapphire. Rubies contain chromic oxide, blue sapphires contain titanium, yellow sapphires contain ferric oxide. Other impure forms are opaque. Corundum stones can produce beautiful asterisms. The word corundum comes from the Tamil word for ruby. Corundum has a specific gravity of 3.96-4.01. COUTURE Highly fashionable clothing and jewelry created by leading designers. CRIMP BEAD A crimp bead is a soft, metal bead through which string (for a bracelet or necklace) is threaded; the crimp bead can be squeezed shut with a pliers to secure the end loops of the threading material fasteners onto the clasps. CROWN The crown is the upper part of a gemstone. CROWN GLASS Crown glass is glass that contains no lead oxide. Some fake rhinestones are made from crown glass. CRYSTAL (GLASS) Crystal is high-quality glass containing at least 10% lead oxide. Lead added to the melt produces very clear glass resembling rock crystal. The process of making lead crystal was discovered by the English glassmaker George Ravenscroft in 1676. Crystal is colored by adding various metallic oxides to the melt. CRYSTAL (NATURAL) A crystal is a solid whose atoms form a very regular structure. Some crystals include quartz, diamond, and emerald. CRYSTAL HABIT Crystal habit is the crystal form that a particular crystal has. The most common crystal habits: CRYSTAL SYSTEMS Crystals are divided into seven crystal systems, according to their optical properties (how light bends within the crystal), plane of symmetry, axis of symmetry, center of symmetry, crystallographic axis. Within each of the systems, the crystals can mineralize into different crystal habits (form). The seven crystal systems are: cubic systems, tetragonal systems, hexagonal systems, trigonal systems, orthorhombic systems, monoclinic systems, and triclinic systems. CUBIC ZIRCONIUM Cubic zirconium (also known as cubic zirconia or cz) is an inexpensive, lab-produced gemstone that resembles a diamond. Cubic zirconia was developed in 1977. CUFF BRACELET A cuff bracelet is a stiff, relatively wide bracelet. The cubic zirconia , hinged cuff seen on catalog from Forever Collection designed by the jewelry designer Lisa Hsieh. CUFFLINKS Cufflinks are men's jewelry that close the buttonholes of the cuff of a long-sleeved shirt. Some cufflinks are basically two button-like objects connected by a chain; the bottons go through the cufff's buttonholes. Another type of cufflink has a decorative button attached to a stick whose end swivels out to form a T-shape that goes through the buttonhole. Cufflinks were first worn in the 1800's. CULET A culet is the bottom point of a gemstone or a small facet that is ground at the base of a brilliant-cut gemstone. The culet prevents splintering of the stone. Modern stones rarely have a faceted culet. CULLINAN DIAMOND The Cullinan diamond (also called the Star of Africa) is the largest diamond yet found, weighing 3,106 carats (roughly 1.3 pounds) in its rough form. It was mined at the Premier Mine in South Africa in 1905. This enormous gem was named for the chairman of the company that owned the mine. It was given to King Edward VII of England for his birthday in 1907. The diamond was cut (by Joseph J. Asscher of Amsterdam) into many stones, including the Cullinan I (530 carats, pendelique-brilliant shaped, the largest cut diamond in the world), the Cullinan II (317 carats, cushion shaped), Cullinan III (94 carats, pendelique shaped), Cullinan IV (63 carats, square-brilliant shaped), and many other smaller stones. CULTURED PEARL Cultured pearls are pearls produced by oysters that have been surgically injected (nucleated) with bits of mussel shell. After 5-7 years, the oysters are retrieved and the pearls are harvested. This method of "manufacturing" pearls was invented in 1893 by Kokichi Mikimoto. CUPID'S DARTS Cupid's Darts is another name for rutilated quartz. CUSHION CUT Cushion cut stones are shaped like a cushion - they have a squarish shape that is rounded on the edges. These stones usually have facets similar to those of a brilliant cut stone. CUT BEADS Cut beads are glass beads that have been faceted. This process makes the bead reflect and refract more light. CUT STONES Common cuts include the brilliant cut, old European cut, emerald cut, radiant cut, rose cut, step cut, pendelique cut. Mixed cuts in which the style of the facets above and below the girdle are different. Other, more unusual cuts, are know as fantasy cuts (like the heart cut). D DANBURITE Danburite (Calcium borosilicate - CaB2Si2O8) is a clear to white silicate mineral whose orthorhombic crystals are transparent to translucent (danburite can also be yellow, greenish, or brown); it resembles topaz. It was named for the city of Danbury in Fairfield County, Connecticut, USA (where the original specimens were found in 1839). Danburite is also found in Russell, New York (USA), Charcas and San Luis Potosi (Mexico), Kyushu Island (Japan), Madagascar, Siberia, Mogok (Myanmar), Bolivia, and Uri (Switzerland). Danburite has a hardness of 7 - 7.3 and a specific gravity of 2.97 - 3.02. Its streak is white DAMASCENING Damascening is the inlaying of a soft metal (like silver or copper) into a hard metal (like steel). The name comes from the city of Damascus, where this process was first used. DARYA-I-NUR Darya-i Nur (meaning "Sea of Light") is one of the largest-known diamonds. It is a flawless, transparent, pink diamond from India, weighing about 175 to 195 carats. It was taken to Persia (now Iran) after Persia's attack on Delhi, India, in l739. The Darya-i Nur is in the crown jewels of Iran, and was worn by the Shah of Iran. DEAD PAWN Dead pawn is an item that was pawned but was never collected by the original owner. DEAD STONE A "dead" stone is a foil-backed rhinestone that has lost its original shininess, usually after water has damaged the foil. For example, a "dead" clear rhinestone will appear dull and off-white, greenish or yellowish. DEAD SOFT Dead soft is a term that refers to very soft-tempered metal. Dead soft wire is the most easily bent wire. For example, copper electrical wire is dead soft. DEMANTOID GARNET Demantoid garnets are valuable green, very lustrous garnets with a cubic crystalline structure. They are a rare variety of andradite. Demantoid garnets have characteristic inclusions that look like horsetails. Demantoid garnets have a hardness of 6-7 and a specific gravity of 3.8 - 3.9. Demantoids were very popular in the 1800's, but are rarely used today. DENDRITIC Dendritic means tree-like, having a branching pattern (like moss agate). DENIM LAPIS Denim lapis is a relatively pale, inexpensive variety of lapis lazuli that is from Chile. It is the color of denim cloth due to calcite inclusions (which whiten the stone and lower its value). DENTELLE Dentelles (meaning "lace" in French) are rhinestones cut with 32 or 64 facets. DEMI-PARURE A demi parure is a matching set of jewelry, usually containing a necklace, earrings, and a pin. See parure. DIADEM A diadem is a tiara, a circular or semi-circular piece of jewelry worn on the head. DIAMANTE Diamante is another word for rhinestone. DIAMOND Diamonds are precious, lustrous gemstones made of highly-compressed carbon. Diamonds are one of the hardest materials known. Diamonds have a hardness of 10, a specific gravity of 3.5, and a refractive index of 2.417 - 2.419. Colors of diamonds range from colorless, yellow, orange, brown, to almost black. Rarer colors are red, blue, green, and purple; these colors (called fancies) are quite valuable. Canary diamonds have a deep yellow color. A diamond's value is based on the "4 C's": color, cut, clarity, and carat weight. A diamond's color (saturation) is rated on an alphabetical scale ranging from D (white) to Y (yellow). "Z" diamonds are fancy, or deep-colored diamond. A diamond's cut is designed to maximize the stone's natural "fire"; brilliant cuts are preferred. A diamond's clarity depends on the number and size of its flaws and inclusions (of other minerals, like quartz). Clarity is rated from FI (flawless), IF (flawless at 10x magnification), a series of V ratings (very small flaws at 10x magnification), a series of S ratings (small flaws at 10x magnification), to I1, I2, and I3 (having inclusions visible to the naked eye). A diamond's carat weight is simple how much it weighs (a carat is about 0.2 grams or about 0.007 ounces). The largest-known gem-quality diamonds include the Cullinan (aka the Star of Africa, 530.20 carats), the Excelsior, the Great Mogul (an ancient Indian diamond which is said to have originally weighed 787.5 carats, but its location is not not known and nothing about it has been authenticated), the Darya-I Nur, the Koh-I Nur, and the Hope diamond (named for its purchaser, Henry Thomas Hope). DIAMOND MELEE Not to be confused with diamond chips, these small diamonds are full cuts, containing all 58 facets, and are frequently used in fine jewelry as accent diamonds. The word melee refers the diamond’s weight, which is less than 1/5 of a carat. DIAPERING Diapering is a crisscross pattern of diamond-shaped lines on a raised-dot enamel pattern. DICHROISM Dichroism is the property of having more than one color, especially when viewed from different angles. Many minerals (like rubies and axinite) are naturally dichroic. This effect can be artificially caused by a thin layer of a metallic oxides that is deposited on the surface of a material. Dichroic coated glass transmits some wavelengths of light and reflecting others, giving it an opal-like appearance. DIE STAMPING Die stamping (also known as machine-stamping) is a process in which sheet metal is cut and shaped between two dies, forming a pattern in relief. Two steel dies are used, the male die has the design in cameo (protruding); the female die has the design hollowed out. The male die is put on top of the metal, the female die is put on the underside of the metal. The press is forcefully brought down onto the dies and metal, forcing the metal into the shape of the mold. Many medallions and mass-produced jewelry findings are made this way. DIFFUSION TREATED Diffusion treated stones are color-enhanced (not naturally colored) stones. The diffusion process only colors the outer surface of the stone, so chipping or re-polishing will result in a loss of color. Diffusion-treated stones are already-cut stones that are heated in the presence of other compounds (like iron oxide, chromium oxide, titanium dioxide, etc.) that will infuse the extreme outer surface stone with color. Under a microscope, you can see the loss of color within each tiny scratch. Diffusion treatment can also change the stone's refractive index. Also, if the stone is faceted, the color will appear stronger where the facets meet. DOG COLLAR A dog collar (also known as "collier de chien") is a type of short, multiple-strand choker-style necklace that fits tightly against the neck. Dog collars are also known as " plaque de cou" (meaning "neck badge") when they are fastened by a clasp in the front. Dog collars are 14"-15" in length. DOUBLET A doublet (also dublette) is a gem made from two layers in order to save expenses; the lower part of the composite stone is glass or a non-precious stone, the top is the more valuable stone. Many different types of doublets have been manufactured (including opal doublets). One common doublet contains a layer of real garnet and a layer of glass. A thin, red garnet top is glued to a colored glass bottom. A green glass bottom with a red garnet top layer produces an emerald-like stone. A diamond is enlarged by cementing it to a crystal base. DOUBLY REFRACTIVE STONE In doubly-refractive stones, the light entering the stone is split into two light rays, and the rays travel in different paths. These stones have more than one refractive index. Calcite, peridot, zircon, tourmaline, and titanite are doubly-refractive stones. Birefringence is another name for double refraction. DROP CUT A drop cut (or briolette) is a pear-shaped cut gemstone with triangular facets on top. This type of stone makes a nice pendant. DROP EARRING Sometimes referred to as a “dangle earring”, this design includes any earring with hangs below the earlobe. DRUZE Druze is a layer of crystals that form within a mineral crust, like the inner cavity of a geode. Amethyst crystals are often found in a druze. The inner cavity of agate geodes are often lined with a druze of sparkling quartz crystals DUCTILE A ductile substance is easily pulled or stretched into a thin wire. gold is the most ductile metal. DUMORTIERITE Dumortierite (Aluminum Boro-silicate Hydroxide) is a blue to violet silicate mineral that is used as an ornamental stone (and sometimes as a semi-precious stone in jewelry). Dumortierite quartz is a massive variety of opaque quartz that is intergrown with dumortierite crystals. Dumortierite has a hardness of 7 - 8.5 and a specific gravity of 3.3 - 3.4.
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