Gemstone Glossary

An alloy is the homogeneous mixture or solid solution of two or more metallic elements or metallic and nonmetallic elements. The alloy is usually achieved by bringing the metals to a molten state under high temperatures and fusing or dissolving them into one solid solution. In jewelry, combining different metals is commonly done to augment the color, hardness and/or luster of the resulting alloy.

Some common alloys used in jewelry manufacturing are:

• Common gold alloys are made by mixing gold, silver, copper, and/or other metals to produce 14K, 18K and 22K gold, white gold (gold and nickel or palladium), rose gold (gold and copper), green gold (gold with silver or silver and cadmium) , and blue gold (a recent gold color told to be perfected by only a few jewelers).
• Sterling silver is a combination of 92.5% silver and 7.5% copper, while coin silver is 80% silver and 20% copper.
• Brass is an alloy typically of 60% copper and 40% zinc.
• Bronze is an alloy of at least 60% copper and tin or other metals.
• Pewter is an alloy of low melting point metals including tin, lead, antimony, bismuth and sometimes a bit of silver or copper. U.S. manufacturer's are required by law to make lead free pewter.
• Niello is a black alloy of silver, copper, lead and sulfur. It is used to fill engraving, imparting an inlaid effect after the metal is fired and polished.

Nickel silver (also called German silver) is a white metal alloy of 70% copper, 20% zinc and 10% nickel. It contains no silver. Many people are allergic to nickel and because of this, the use of nickel silver in jewelry has been outlawed in some countries.  

A small magically empowered object, worn around the neck or carried to ward off evil, harm, or illness. May also be worn to bring good fortune and protection from harm. A charm, fetish or good-luck piece.

Some common amulets:

• The scarab amulet was sacred to the Egyptians and symbolized rebirth. 

• The Ankh is an Egyptian amulet which symbolized eternal life. It is thought to be the oldest and most sacred Egyptian amulet. 

• The Eye of Horus amulet was believed to protect the wearer from evil in life and in the Afterlife.  

Also see talisman.

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A bezel setting is a technique of setting a stone in jewelry. The stone is held in place by first soldering the bezel, or metal ring, to the base of the piece. Next, the stone is inserted and the metal is compressed tightly around the stone to hold it securely.

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A rock or gemstone associated with the calendar month of birth or a sign of the Zodiac. The origin of birthstones is said to be based on the Breastplate of Aaron which is described in Exodus 28, 15-30. Instructions for fabricating the Breastplate called for the twelve stones of the Twelve Tribes of Israel to be set in four rows. These gemstones corresponded to the zodiac signs of the time.

There are many versions of birthstone charts going back to ancient times. On our site we have included most of them.

• Modern birthstones - This is the official list from the American National Association of Jewelers, Jewelers of America officially adopted it in 1912.
• Traditional birthstones - usually a compilation of the most common birthstones from ancient cultures, choosing the most common gem
• Mystical birthstones - a list of Tibetan origin which dates back more than one thousand years and holds great power
• Ayurvedic birthstones - from Indian medicine, legend, lore and beliefs dating back to ancient India (circa 1500 BC)
• Zodiac birthstones - stones assigned to each of the twelve signs of the Zodiac, which one might also consider Talismanic stones
• Ancient birthstones - A chart listing of Arabic, Hebrew, Hindu, Italian, Polish, Roman and Russian birthstones throughout history
• Planetary birthstones - stones that are associated with each of the planets
• Talismanic birthstones - talismans believed to have magical powers and to protect the wearer against evil. Specific stones corresponding to each sign of the Zodiac, so these are the stones you would wear for your zodiac sign for protection from all things evil.

Check out our Birthstone/Anniversary Stone Page!

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Cabochon

A stone which has been cut and polished to have a a domed upper  surface and a flat base. It may be high domed or almost flat and can be cut into any shape. A cabochon has no facets. This is one of the oldest and simplest types of cuts and it is called en cabochon. This form of cutting is most often used on stones like turquoise, lapis, opals, various forms of quartz and other opaque and semi-opaque stones.

Calibrated

A calibrated stone is one that has been cut exactly to a standard size, i.e. 5 mm, 10 mm x 14 mm. Jewelers often purchase calibrated cabochons or faceted stones when the design requires two or more stones of the same exact size or when a design will be duplicated many times as in manufactured jewelry.

Carat

Carat (ct.) is the standard measure of weight used for gemstones. One carat weighs 0.2 gram (1/5 of a gram or 0.0007 ounce). A hundredth of a carat is called a point. Note that karat is the term used to describe the fineness of gold and carat is used for weight.

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Cast or Casting

Intricate patterns and shapes can be carved into wax from which a mold is made. Casting is the actual process of making jewelry by pouring molten metal into such a mold. This process is used both to create one of a kind items and is used extensively to mass produce less expensive jewelry items.

Cleavage

Cloisonné

Cloisonné is a technique in which colors of a design are kept apart by thin metal strips that are placed on a base. Metal filaments are then attached, to outline the design. Then these areas are filled with colored enamel and heated at high temperatures to fuse the enamel to the surface.

It is believed that Cloisonné originated in Beijing during the Yuan Dynasty (1271-1368). The process was improved and advanced during the Ming dynasty (1426-1456) and further perfected during the Qing Dynasty (1736-1795), but is currently practiced worldwide.

Also, see enamel and plique-a-jour. 

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Dichroic Glass

A glass which contains ultra-thin layers of aluminum, chromium, silicon, zirconium or the metal alloy titanium. The colors are almost holographic in appearance. Addition of the various elements is what produces the bold and dramatic colors. Colloidal gold may also be added. The appearance will be different depending on whether the light is reflected or transmitted.

More information from Brian Kerkvliet on the mysteries of dichroic glass.

Diffusion

Diffusion is the process of color enhancing a stone by heating the stone in the presence of iron oxide, chrome oxide or similar compounds. The process colors the stone by infusing the outside surface of the stone with color. Only applied to cut stones as any further cutting would remove the color enhancement. This process is often used on sapphires and topaz to heighten or alter the colors.

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Dull

The term used to describe gems which exhibit an earthy or dull luster, meaning their surface does not reflect light very well. Plastic can be described as having a dull luster as is clay. Hematite that does not have a highly polished surface will display a dull luster.

dwt.

A measure of Troy weight, dwt. is the abbreviation for "pennyweight", a measure used to weigh gold, silver, and jewels. In Troy weight, the pound = 12 ounces, the ounce = 20 pennyweights, and the pennyweight = 24 grains. While this method of weighing is believed to have originated in Cairo during the crusades, the name comes from Troyes, France where it was first used .

Enamel

This is a technique used to add decorative color to metals. Made up of a vitreous pigment of metallic oxide mixed with powdered glass, it is fused to the surface of a metal like copper, bronze, silver or gold under very high temperatures. The colors and transparency of the fused glass will depend on the metal oxides used and the temperature during firing. Also, see cloisonné and plique-a-jour.

Facet

One of the flat polished surfaces cut on a gemstone which allow the cut stone to sparkle and reflect light. Diamonds, emeralds, sapphires, and rubies are normally faceted.

Fire

Fire in a stone refers to the streaks and flashes of brilliant color(s) seen when the stone is rotated or moved in a natural or artificial light source. Opals are noted for their fire.

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Freeform

A stone cut in an unusual or non-calibrated shape, or that is left in it's natural state and then polished.  It is a shape that is non uniform.

Gemstone

Today, the common definition of a gemstone is any precious or semi-precious stone, rock or mineral.

The explicit definition of a gemstone is a precious stone: diamond, ruby, sapphire, emerald and precious opal, although that is a common misrepresentation.

Semiprecious stones are any other rocks, minerals, or petrified material that is not classified as precious and which is used in jewelry or collected, this is also called "gem quality". Some semi-precious stones include: agate, topaz, carnelian, jasper, lapis lazuli, jade and turquoise.

Greasy

Used to describe a gemstone's luster. Some gems which can exhibit a greasy luster are: nephrite jade, jadeite, soapstone, and talc.

Hallmark

A hallmark is the official mark stamped or inscribed in metal which indicates the fineness of the metal and the manufacturer. For example, a hallmark of 925 indicates the piece is 92.5% fine silver while a mark of 14K indicates the piece is 14/24 gold (see karat). Hallmarks also indicate the maker of the piece. In Britain, a hallmark is required by law and it is illegal to incorrectly mark the metal content. In the United States hallmarks are not required by law, but are customarily used by artists and designers.

The word hallmark originated in the Middle Ages in England, when silversmiths were members of the Guildhall, hence "Hall"mark..

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Hardness

Hardness is measured using the Mohs Scale of Hardness. A substance's hardness value indicates the materials resistance to scratching and grades minerals on a comparative scale from 1 (very soft) to 10 (very hard).. In the Mohs scale, a mineral of a given hardness rating will scratch other minerals of the same rating, as well as any minerals of a lower rating. For example, sapphires and rubies have a Mohs rating of 9 and will scratch each other, as well as any mineral with a rating lower than 9. However, they will not scratch diamonds, which are rated 10. The Mohs scale of mineral hardness was devised by the German mineralogist Frederich Mohs (1773-1839) in 1812.Check out the Mohs Harness Scale.

Inclusion

In gemstones, an inclusion is any solid, liquid, or gaseous foreign body enclosed in the mineral or rock. The price of amber can vary greatly based on the type of inclusions and clarity of the stone. Amber that contains complete bodies of prehistoric bugs or a well defined fern or leaf can bring a high price, while small bubbles of gas/liquid add only interest to the stone but do not increase the value significantly.

Quartz is another clear stone that when embedded with well defined needle like rutile inclusions can demand a high value.

Inlay

Inlay is a decorative technique using stone, mother of pearl or even glass. It is embedded into another material such as metal or wood resulting in a level surface of the two materials. Inlay is used in jewelry with stones and in furniture with stone or different woods to create a design.

The Zuni Indians used this technique in their jewelry by making a mosaic of different colored stones and bezel setting them in rings, bracelets and pendants.

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Intaglio

An Intaglio is a carving where a design is cut or carved into stone or metal so that the carving is below the surface of the material. A cameo is the opposite where the design is carved in relief from the background. This technique was commonly used for seals which were dipped in wax and used to seal a letter or document.

Some of the most common intaglios were carved in the gemstone carnelian and used for signet rings. The earliest known signet rings date back to ancient Egypt.

Iridescent

A gem displaying rainbow-like colors is called iridescent. Iridescence is caused by the reflection of light from the jewel. Mother of pearl is one example of iridescence used in jewelry.

Karat

Karat (abbreviated Kt or K) is the measure of the fineness of gold equal to 1/24 part. Pure gold is 24 karat gold, 18K gold is 18/24 gold, 14K gold is 14/24 gold, 12K gold is 12/12 (exactly half gold). Note that the term carat is used as measure of weight for gemstones.

Keum Boo

A jewelry-making technique from Korea where 24k gold foil is fused to sterling silver.

Lapidary

Lapidary is the art of collecting and cutting gemstones. A lapidary is one who cuts and polishes stones to bring out their true beauty.

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Lariat

A necklace without a clasp, worn looped around the neck with open ends that may be tied into a loose knot, (or lariat) fastened with a ring or a brooch, or tied with a "lariat loop".

Luster

A stone's or mineral's  luster is its glow or sheen, the result of the way it reflects light, and can help identify it. Luster is dependent on both the stone's surface (polish) and the reflective index of the mineral. Gemologists use many terms to describe luster: adamantine, pearly, greasy, metallic, silky, resinous, vitreous, earthy or dull, and waxy.

Two of the most common lusters are vitreous and metallic. Vitreous luster is glassy, like a quartz crystal or a water glass. Metallic luster is metallic like a metal wire.

Some other lusters that are used are:
Adamantine - has a high degree of sparkle like a diamond.
Earthy or Dull - does not reflect much light.
Pearly - similar to a pearl in the way it reflects light
Resinous - similar to resin in the way it reflects light
Silky - similar to silk in the way it reflect light

The Mohs scale of mineral hardness was devised by Frederich Mohs, a German mineralogist, in 1812. To devise the scale, he selected ten minerals as a basis because they were common or readily available, thus the scale is not linear, but is a bit arbitrary. The Mohs scale is still the most common scale of mineral hardness in use today.  The Mohs Scale of Hardness measures a substance's hardness or how resistant it is to being scratched. The scale ranges from 1 to 10. 

You can test a mineral's hardness by doing a scratch test to compare it to the mineral types on the Mohs scale. If an item scratches the mineral type, it is harder than that mineral. If it does not scratch that mineral type, it is softer than that mineral. Half ratings (e.g., 5.5) come from when a mineral does scratch one mineral but does not scratch the next hardest mineral on the Mohs scale.

 

Hardness	Mineral	Associations and Uses
1	Talc	Talcum powder.
2	Gypsum	Plaster of paris. Gypsum is formed when seawater evaporates from the Earth’s surface.
3	Calcite	Limestone and most shells contain calcite. Calcite
4	Fluorite	A mulit colored gemstone. Fluorite
5	Apatite	A beautiful teal blue gemstone. Apatite
6	Orthoclase	Orthoclase is a feldspar, and in German, "feld" means "field".
7	Quartz	There are many forms of quartz.
8	Topaz Beryls	Beryls include Aquamarine and Emerald. Topaz
9	Corundum	Sapphire and Ruby are varieties of corundum. Twice as hard as topaz.
10	Diamond	Used in jewelry and cutting tools. Four times as hard as corundum.

Hardness of other relate able items:

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This is a term applied to stones which are made by using small chips, powder and ground up low grade stones, binding or fusing them with a plastic resin (epoxy) and compressing them into blocks. The blocks are then cut into beads, cabochons, and slabs.

In some cases, the reconstituted stone is actually made from real turquoise, amber, lapis or similar stone, but often the reconstituted stones are nothing more than low grade rocks, like howlite, that have been dyed and compressed to look like the real gemstone.

Ambroid is a form of reconstituted amber made from real amber pieces, but should be classified as imitation because of the epoxy resin content. It is made from scraps and shavings of amber that are heated and pressed into large blocks. Insects found in ambroid are usually fully intact, without broken body parts, as they were dead when added to the block. Insects found in real amber usually have broken wings and legs caused when they tried to escape from the sticky tree resin.

Reconstituted turquoise is manmade from pulverized pieces of turquoise that are stabilized and compressed with plastic resins to which dye is added and should be sold as "simulated" or "imitation" turquoise. However, this form is often used in much of the mass produced inlay jewelry.

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Used in the jewelry making process to create a textured surface with ridges, ripples and valleys. The process requires deft use of a torch to bring the metal to a high temperature just below its actual melting point. The jeweler carefully moves the torch flame around the metal surface, "pulling" the almost flowing metal into various ridges.

This takes extreme concentration and patience, allowing the torch to remain directed in one area for a split second too long will cause the metal to melt and either form a hole or a "ball" of molten metal instead of realizing the desired effect. The pattern of valleys and ridges of a reticulated piece is unpredictable and trying to duplicate a pattern is impossible although a skillful craftsperson will be able to create something similar to the original.

Also called labradorescence, it is a colorful play of light across the cleavage planes that is displayed in some minerals. The term labradorescence is derived from the mineral Labradorite which displays this attribute.

Spectrolite, the form of labradorite found only in Finland, has the most vibrant colors ranging from light blue, aqua, green, gold and red to dark blues, with some exceptional stones that exhibit all of these colors.

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