EnchantedLearning.com Rock and Mineral Dictionary

The one dollar US Sacajawea coin. Although it appears to be made of gold, it is not! It is an alloy of copper, zinc, manganese, and nickel.

Gold is a precious metal that has been valued by people since ancient times. People use gold for coins, jewelry, ornaments, and many industrial purposes. Until recently, gold reserves formed the basis of world monetary systems.

Gold is a very soft metal when it is pure (24 Kt. is pure gold). Gold is the most malleable (hammerable) and ductile (able to be made into wire) metal. Gold is usually alloyed (mixed with other metals, often silver and copper) to make it less expensive and harder. The scientific abbreviation of gold is Au.

The purity of gold jewelry is measured in karats. Some countries hallmark gold with a three-digit number that indicates the parts per thousand of gold. In this system, "750" means 750/1000 gold (equal to 18K); "500" means 500/1000 gold (equal to 12K).

Karat	Percent Gold
24 Kt.	100% Gold
18 Kt.	75% Gold
14 Kt.	58.3% Gold
10 Kt.	41.7%

Alloyed gold comes in many colors:

Colored Gold	Alloy Metal(s) Added to the Gold
Yellow Gold	50% silver and 50% copper
White Gold	Nickel, zinc, copper, tin and manganese
Pink (rose) Gold	90% copper and 10% silver
Green Gold	High proportion of silver or cadmium
Blue Gold	Some iron
Grey Gold	15-20% iron

A Glossary of Gold-Related Terms:

AQUA REGIA Aqua regia is a 3:1 mixture of hydrochloric acid and nitric acid. Aqua regia is used to test gold and platinum; it is one of the few substances that can dissolve gold and platinum.

ASSAY An assay is a test of the purity of an alloy. A tiny piece of metal is scraped from the piece and the percentage of gold or silver is determined. Official assay offices determine whether a piece qualifies for an appropriate hallmark.

BLACK HILLS GOLD Black Hills gold is gold jewelry that is made (but not always mined) in the Black Hills area of South Dakota, USA. Gold was first discovered in that area about 1874 by Horatio N. Ross. E.O Lampinen opened the Black Hills Jewelry Manufacturing Company in Deadwood, South Dakota in the early 1900's. Modern day Black Hills jewelry often has a three-color (yellow gold, pink gold and green gold) grape leaf and vine pattern. There are many companies that make Black Hills jewelry today, but by law, their creations must be made from Black Hills gold. This jewelry is often (but not always) 10 Karat gold.

BLUE GOLD Blue gold is gold with a bluish tinge. It has been alloyed with a mix that includes iron.

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.

DUCTILE A ductile substance is easily pulled or stretched into a thin wire. Gold is the most ductile metal.

ELECTROPLATE Electroplating (also called Galvanotechnics after its inventor, Luigi Galvani) is a process in which one metal is coated with another metal using electricity. In jewelry, inexpensive metals are frequently electroplated with more expensive metals, like gold (gold plating), copper (electrocoppering), rhodium (rhodanizing), chromium (chromium plating), or silver (silver plating). The thickness of the metal coat varies. Electrogilded coating is the thinnest (less than 0.000007 inches thick); gold-cased metals have a coating thicker that 0.000007 inches.

ELECTRUM Electrum is an amber-colored alloy of gold and silver that was was used in ancient times. Electrum is also an alloy used in medieval times consisting of copper (50%), nickel (30%) and zinc (20%).

FINENESS Fineness is the proportion of silver or gold in a metal alloy. Fineness is usually expressed in parts per thousand. For example, the fineness of sterling silver is 925.

FOOL'S GOLD Fool's gold is pyrite, a shiny, metallic mineral that looks like gold, but is actually a a form of iron. Marcasite stones come from pyrite.

GOLD DORE Gold doré (pronounced gold doh-rey) is a bar of semi-purified gold (e.g. bullion). After being mined, the first stage in the purification process of the gold ore produces a cast bar (gold dore) that is approximately 90% gold. The other 10% is mostly metals like silver and copper.

GOLD FILLED Gold filled (abbreviated G.F. or written as "doublé d'or") jewelry is made of a thin outer layer of gold atop a base metal. For example, jewelry marked 1/20 G.F. 12 Kt. is at least 1/20th gold and is layered with 12 karat gold. To be classified as gold-filled, a piece must be at least 1/20 gold by weight.

GOLD PLATED Gold-plated metal has a very thin layer of gold on the surface, usually applied by the process of electroplating. Pieces that are gold plated are often marked G.E.P., gold electroplate, gold plated, or electro-plaqué d'or.

GOLD STONE Goldstone (also known as aventurine) is a shimmering quartz stone that ranges in color from yellow to red to light green to light brown. The shimmer is caused by tiny metallic particles (mica) within the stone (not gold).

GREEN GOLD Green gold is gold that has been alloyed with a higher percentage of silver than copper.

GREY GOLD Grey gold is gold that has been alloyed with 15-20% iron.

HALLMARK A hallmark is an official mark (or a series of marks) made in metal that indicates the fineness of the metal and the manufacturer's mark. For example, a hallmark of 925 indicates 925 parts of gold per 1000 weight. Other hallmarks indicate the maker of the piece and sometimes the year of manufacture. In many countries (like Britain) it is illegal to hallmark metal incorrectly; some countries are notoriously lax in their enforcement of hallmark honesty.

Karat Percent Gold 24 Kt. 100% Gold 18 Kt. 75% Gold 14 Kt. 58.3% Gold 10 Kt. 41.7% KARAT Karat (abbreviated Kt) is a measure of the fineness of gold. 24 karat gold is pure gold. 18 karat gold is 18/24 gold (about 75% gold - three quarters gold). 14 karat gold is 14/24 gold (about 58% gold - a little over half gold). 12 karat gold is exactly half gold. 10 karat gold is 10/24 gold (only about 43.5% gold - less than half gold).

KARATCLAD Karatclad is a trademark for a very thick gold electroplating process; this type of plating is about 14 times thicker than standard electroplating.

LEAF Metallic leaf is paper-thin sheets of metals. For example, Gold, silver, platinum, and copper are rolled or pounded into metallic leaf which can be applied to surfaces.

MALLEABLE Malleable metals are easily worked with a hammer or a roller. Gold and sterling silver are very malleable metals.

NOBLE METALS The noble metals are gold, platinum, and silver. These are metals that are relatively impervious to chemical action.

PINCHBECK Pinchbeck (also known as "false gold") is a alloy of copper that looks like gold. Pinchbeck was invented by the British watchmaker Christopher Pinchbeck (1672-1732) in the early 18th century. Pinchbeck consists of 83% copper and 17% zinc. Ironically, there have been many imitations of Pinchbeck (which itself is an imitation).

PINK GOLD Pink gold (also known as rose gold) is gold with a tinge of pink. It has been alloyed with a mix of 90% copper and 10% silver.

PLATING Plating or electroplating (also called Galvanotechnics after its inventor, Luigi Galvani) is a process in which one metal is coated with another metal using electricity. In jewelry, inexpensive metals are frequently electroplated with more expensive metals, like gold (gold plating), copper (electrocoppering), rhodium (rhodanizing), chromium (chromium plating), or silver (silver plating). The thickness of the metal coat varies. Electrogilded coating is the thinnest (less than 0.000007 inches thick); gold-cased metals have a coating thicker that 0.000007 inches.

PYRITE Pyrite (also known as fool's gold) is a shiny, metallic mineral that is a form of iron. Marcasite stones come from pyrite.

ROLLED GOLD Rolled gold is a very thin sheet of gold that is laminated to a lesser metal (usually brass). The two layers of metal are heated under pressure to fuse them together. The sheet is them rolled into a very thin sheet and then used to make jewelry or other objects. Jewelry made from rolled gold wear well over time. Rolled gold pieces are marked rolled gold plate, R.G.P., or plaqué d'or laminé.

ROSE GOLD Rose gold (also known as pink gold) is gold with a pink tinge. It has been alloyed with a mix of 90% copper and 10% silver.

RUSSIAN GOLD FINISH A Russian gold finish is a matte, antique-look finish.

Troy Unit Equivalence 1 pennyweight 24 grains = 1.5552 grams 1 Troy ounce = 20 pennyweight 31.1035 grams 1 Troy pound = 12 Troy ounces 373.24 grams TROY WEIGHT Precious metals (like gold, platinum, and silver) are measured in troy weight, which has units of pennyweights, ounces, and pounds. Troy ounces and pounds are different from everyday US measures.

VERMEIL Vermeil is gold-plated silver. Less occasionally, gold-plated bronze is referred to as vermeil.

WHITE GOLD White gold is gold that has been alloyed with a mix of nickel, zinc, copper, tin, and manganese.

YELLOW GOLD Yellow gold is gold that has been alloyed with a mix of 50% copper and 50% silver.

YGF YGF is an abbreviation for yellow gold filled.

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