There are many useful terms that help to understand the use of precious metals like gold, platinum, and silver as they exist in nature and have been used in jewelry throughout time. This glossary features an extensive listing of terms related to precious metals, and will help to provide context and further information about everything that has been presented on our Precious Metals pages.
Aigrette: a feathered hair ornament.
Alchemy: a mixture of science and magic practiced for over 1500 years. Alchemy focused predominantly on finding the elixir of life and turning base metals into gold. It was a precursor to the modern disciplines of medicine and chemistry.
Alloy: a mixture of two or more metals.
Alluvial gold: gold that is found in riverbeds or on coastal beaches, sometimes a great distance from the lode from which it came.
Amalgam: an alloy of mercury and another metal.
Annealing: heating metal to change its microstructure and restore its strength and hardness.
Aqua regia: a mixture of three parts hydrochloric acid and one part nitric acid. Aqua regia, or “royal water,” was so named because it is the only acid that can dissolve gold, the “royal metal.” It is used to test the fineness of gold alloys in the higher karatages, and to refine platinum from mineral ores.
Assay: a test to determine a metal’s purity.
Base metal: a non-precious metal such as copper, iron, nickel, or zinc.
Billion: a precious metal alloy (typically silver, but sometimes gold) which is primarily comprised of a base metal (such as copper). The word is derived from the Latin, billo, a coin containing mostly copper.
Britannia metal: a silver pewter-like metal that contains mostly tin, but no silver.
Britannia silver: a silver alloy comprised of 95.84% silver and 4.16% percent copper.
Bullion: precious metals in bulk form. Used for investment purposes and traded in commodities markets.
Bullion coin: a coin used for investment purposes. The worth is based on the value of their troy weight and the market price of the metal they contain.
Cabochon: a non-faceted gemstone that has a polished dome.
Chinese silver: an alloy made of 58 percent copper, 17.5 percent zinc, 11.5 percent nickel, 11 percent cobalt, and 2 percent silver.
Coin silver: a silver stock created by melting coins. It is usually comprised of 90 percent silver and 10 percent copper.
Collector’s coins: coins whose value is determined by a variety of factors including age, rarity, and condition.
Commemorative coin: a type of collector’s coin that is issued in honor of important events, people, or places.
Cupel: a small, porous vessel used in the assaying process.
Cupellation: a method for assaying, or testing the purity of metals. Historically, it was also the means of extracting silver from lead.
Debasement: overcoming a shortage of monetary metals by reducing the size or precious metal base of established coinage.
Die: engraved stamp used for impressing a design.
Ductile: capable of being fashioned into a new shape without fracture. This means a metal can be elongated or drawn into fine wire without breaking.
Durability: a substance’s ability to withstand heat, chemicals, and wear.
Electrum: a naturally occurring alloy of gold and silver.
Eluvial gold: gold that is found under the soil near the lode from which it came.
Findings: a small accessory or component used to make up a finished piece of jewelry (e.g., heads, shanks, clasps, etc.).
Fine gold: gold containing no other elements or metals. It is also called pure gold or 24K gold and it has a fineness of 999.
Fine silver: silver with a purity of 99.9 percent or better.
Fineness: a measure of purity for precious metal alloys. It is the amount of gold, silver, or platinum in relation to 1000 parts. For example, gold with a fineness of 750 has 750 parts (75%) gold and 250 (25%) parts other metals.
Finishing: the process of cleaning and polishing an item of jewelry. Tool marks are removed, edges are smoothed, luster is achieved or other surface effects are applied.
Firescale: a term for the red or purple color that appears on sterling silver when it is heated to high temperatures.
German silver: another name for nickel silver, a metal that has no silver content but is composed of nickel, copper and, occasionally zinc.
Gilding: applying gold leaf to a surface, usually metal or wood.
Hallmark: an official mark made by an independent third party, often an assay office, to certify or guarantee the purity of a precious metal object.
Head: the part of a mount that holds gemstones.
Heft: the relative heaviness of an object when it is lifted or handled.
Karat gold: a gold alloy, which in the U.S. must have a fineness of at least 10K. In Britain and Canada, it must be at least 9K.
Karatage: a measure of the purity of gold. One karat is 1/24 pure, so 24 karat is pure gold. Karat is abbreviated as “K” or “Kt.” Outside the U.S. “karat” is often spelled “carat,” but this should not be confused with the unit of weight for gemstones also called measured in “carats.”
Lavalier: originally this term referred to a necklace with two pendants of unequal length suspended from it–also called a negligee pendant. More recently, it has become a generic term for a drop pendant.
Luster: the appearance of a material’s surface in reflected light–as in the sheen of a metal that has been polished.
Malleable: an ability to be stretched in all directions without breaking. This means a metal can be rolled and hammered into extremely thin sheets.
Matte: an impure product of the smelting of certain ores (e.g., platinum).
Metal memory: a characteristic of metal which quantifies the extent to which it retains a new shape once it is formed.
Mexican silver: a silver alloy used in Mexico from approximately 1930 to 1945, which is comprised of 95 to 98 percent pure silver.
Mounting: the precious metal part of a piece of jewelry before stones are set into it.
Native platinum: grains or nuggets of pure or nearly pure platinum.
Native silver: rare nuggets of pure or nearly pure silver.
Negative tolerance: the allowable difference in the fineness indicated by the mark and the actual fineness of the object. The U.S., for example, permits a difference of three parts per thousand on unsoldered items and seven parts per thousand on soldered items. This means that a soldered 18K (750) gold ring can have a fineness as low as 743 and still be marked 18K.
Noble metal: a metal that resists corrosion and tarnishing.
Ore: rock containing valuable minerals in sufficient concentrations to be profitably mined, transported, milled, and processed.
Parting: the separation of gold from silver in a refining protocol.
Patina: a pleasant surface sheen on an object or metal, which forms from age or frequent handling. Also a thin layer formed by corrosion on the surface of some metals such as copper and bronze.
Precious metals: metals valued in jewelry making, e.g., gold, platinum, and silver.
Placer deposit: a deposit of sand or gravel that contains precious metals.
Porosity: a metal defect that appears as pits or holes in the surface.
Quality mark: a stamp that indicates the purity or fineness of a precious metal.
Rarity: the characteristic of being uncommon. For precious metals, it refers to their relative concentrations in the Earth’s crust.
Reef: a gold-bearing lode or vein.
Refining: the process of removing impurities from a precious metal.
Rush: a period of feverish influx of people into an area where new sources of precious metals have been discovered.
Sautoirs: long chains or ropes of pearls that have tassels at the ends.
Schwerter’s solution: a solution containing nitric acid, potassium dichromate, and distilled water which is used to test the fineness of silver and the identity of other metals.
Shank: the band of a ring, or the part of the ring that encircles the finger.
Solder: a metal or metal alloy used to join metals together.
Sterling silver: an alloy of 92.5 percent silver and 7.25 percent copper commonly used in the jewelry trade.
Tarnish: the process of corrosion that occurs on some metals (e.g., silver) when they undergo oxidation.
Touchstone test: an assay that compares how precious metal alloys of known and unknown fineness react to acid.
Underkarating: an illegal misrepresentation of the precious metal content of a piece of jewelry.