Whether it’s understanding gemological or jewelry terms in an article you’re reading or simply gaining a greater understanding of the world of jewelry and gemstones, our Jewelry & Gem Dictionary is a handy reference guide. And, unlike most dictionaries, ours makes for interesting reading all on its own!
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 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 (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 Prrsia (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 is an item that was pawned but was never collected by the original owner.
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 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 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 means tree-like, having a branching pattern (like moss agate).
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).
Dentelles (meaning “lace” in French) are rhinestones cut with 32 or 64 facets.
A demiparure is a matching set of jewelry, usually containing a necklace, earrings, and a pin.
Water has a density of 1gram/cc. Density is the weight of a material as compared to an equal volume of water.
The height of a gemstone measured from the culet to the table.
The height of a gemstone, measured from the culet to the table, divided by the width of the gemstone. The depth percentage is critical to creating brilliance and fire in a diamond, and a gemstone with a depth percentage too low or too high will lack sparkle.
A diadem is a tiara, a circular or semi-circular piece of jewelry worn on the head.
Diamante is another word for rhinestone.
The width of a diamond, as measured across the widest part of the girdle.
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).
Diapering is a crisscross pattern of diamond-shaped lines on a raised-dot enamel pattern.
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 (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 stones are color-enhanced (not naturally colored) stones. The diffusion process only colors the outer surface of the stone, so chipping or repolishing 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 stonger where the facets meet.
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.
A doublet (also dublette) is a form of gemstone trickery devised to allow inexpensive materials to imitate the more valuable gemstones before modern synthetics were available. A doublet can take several forms but always involves a fake gemstone produced by gluing together two different materials to form an illusion. A very common one in Victorian times was the garnet and glass doublet. This involved a red garnet top, glued to a colored glass bottom. The refractive properties of a faceted stone are such that the red of the garnet only shows at odd angles, or if the stone is immersed in a special liquid with a high refractive index. Thus, for example, a green glass bottom with a garnet top will give the appearance of a fine emerald because the top is a natural gemstone with cut facets, and a few natural imperfections, and the bottom is bright green which reflects throughout the stone. The effect is hard to appreciate unless you have seen one.
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.
A drop cut (or briolette) is a pear-shaped cut gemstone with triangular facets on top. This type of stone makes a nice pendant.
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
A ductile substance is easily pulled or stretched into a thin wire. gold is the most ductile metal.
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.