Gold

Major part of only a few rare metals

Gold is a pleasure to own and possess, as many people have discovered throughout the ages and around the world. Gold is a very stubborn element when it comes to reacting to or combining with other elements. Keeping this in mind, helps to explain many things about gold. There are very few true gold ores, besides native gold, because it forms a major part of only a few rare minerals, it is found as little more than a trace in a few others or it is alloyed to a small extent with other metals such as silver. Gold is almost indestructible and has been used and then reused for centuries to the extent that all gold of known existence is almost equal to all the gold that has ever been mined. Gold is a great medium metal for jewelry, as it never tarnishes. Native gold wires emerging from massive white quartz can make for a visually stunning specimen.

A few of the minerals that bear gold in their respective formulas are in a subclass of sulfides called the tellurides. The element gold seems to have an affinity for tellurium and this is one of the only elements that gold can bond with easily. In fact only a few rare tellurides are found with out gold. A few of the tellurides are nagyagite, calaverite, sylvanite and krennerite. These are all minor ores of gold but their contributions to the supply of gold pales next to native gold's own contribution. Occassionally these minerals are associated with native gold.

There are a number of minerals that are aptly named "Fool's Gold" because only a fool could believe they are gold! Actually it is easy for people who see shiny golden colored flakes sparkling at them from some rock they just picked up to believe that they have struck pay-dirt. Gold's ductility, sectility, density and softness are usually sufficient to distinguish it from the much cheaper imposters. The most famous "fool's gold" is the very common sulfide, pyrite. Chalcopyrite, marcasite and just about any golden colored sulfide has been also proven to be worthy the "fool's gold" monicure. Weathered flakes of biotite which can sport a bright yellow color and a nice flash of light when viewed just right, have also been mistaken for gold.

Gold specimens are sometimes artisticly stunning and a good investment as well. After all, it is gold, which never seems to lose its value. Good natural specimens though are more expensive than their actual weight value. This is to be expected as good gold crystals are somewhat scarce (most are melted down for quick profits) and you really don't want a natural specimen to be worth what a lump of previously smelted and refined gold is worth, do you?.

Troy Weight
Used in weighing the precious metals.
24 grains = 1 pennyweight (dwt.)
20 dwt = 1 ounce Troy
12 ounces = 1 pound Troy
5760 grains = 1 pound Troy
480 grains = 1 Troy oz.

1 kilogram = 2.68 pounds
1 kilogram = 32.15 Troy oz.
1 kilogram = 2.2046 lbs. Avoir
1 kilogram = 35.2740 oz. Avoir
1 kilogram = 15,432 grains

Troy oz. – 1.0972 Avoir oz.

Avoirdupois Weight
Used in weighing base metals.
16 drams (or drachms) = 1 oz. Avoir
16 ounces = 1 pound Avoir
16 ounces = 7,000 grains
28 pounds = 1 quarter English
4 quarters = 1 hundredweight (cwt.)
20 hundredweight = 1 ton Avoir 1 pound Avoir = 14.5833 Troy oz.
1 ounce Avoir = 0.914 Troy oz.
1 pound Avoir = 7,000 grains
1 ounce Avoir = 437.5 grains
1 pound Avoir = .4359 kilo.

Gram Weight
1 gram = 15.43 grains Troy
1.555 grams = 1 pennyweight (dwt.)
31.104 grams = 1 ounce Troy
28.35 grams = 1 ounce Avoir 1 grain = 0.0648 grams
1 grain = 64.80 milligrams
1 milligram = .015432 grams
1 gram = .035274 Avoir oz.
1 gram = .032151 Troy oz.

Pure gold (fine gold) is softer than pure silver but harder than tin. Its beauty and luster are unmatched by any alloyed golds. The extreme malleability, ductility, and softness of pure gold make it practically useless for jewelry applications.

The addition of alloying elements (other metals) to gold are used to increase the toughness and hardness of the metal. While almost any metal can be alloyed (melted) with gold, only certain metals will not dramatically change the color or make the metal brittle. The addition of indium, for instance, turns gold purple and gives gold the workability of glass.

Over time, certain percentages of gold have become legally recognized "karats." The karat indicates the amount of gold as a percentage of the total, i.e. 24 karat is 100 percent gold. Thus 14 karat is 14/24's gold or 58-1/3 percent gold. Gold standards vary around the world. In the United States, 18, 14, and 10 karat gold are the only karats allowed to be sold as karated gold.

In karated gold, there is a balance of metals in the non-gold percentage. These metals provide the various colors and hardness of karated golds. Typical alloying elements and their color effect are:

Copper Reddening
Silver Greening
Zinc Bleaching
Nickel Whitening
Palladium Whitening

Examples of the compositions of different colors are:
Yellow Gold, copper, silver, zinc
White Gold, copper, nickel, zinc
Red Gold, copper
Green Gold, silver

Adjusting the proportions of coloring agents provides the array of colors on the market. Additional metals enhance properties such as castability, grain size, hardness, corrosion resistance, color, workability, ultimate strength, and others. These additions can dramatically change the properties of the karated metal for better or worse.

Knowing how the additions will affect the metal greatly enhances the possibility of a superior final product. In deep drawing of metals, it is important to have a metal which will elongate or stretch a great deal before fracturing, thus high ductility. The requirement for an earring post would be a high tensile strength (a great deal of force needed to get the material to permanently deform, bend). It is imperative to select the proper karated composition for the desired application.

PHYSICAL CHARACTERISTICS:

• Color is golden "butter" yellow.
• Luster is metallic.
• Transparency is opaque.
• Crystal System is isometric; 4/m bar 3 2/m
• Crystal Habits include massive nuggets and disseminated grains. Also wires, dendritic and arborescent crystal clusters.
• Cleavage is absent.
• Fracture is jagged.
• Streak is golden yellow.
• Hardness is 2.5 - 3
• Specific Gravity is 19.3+ (extremely heavy even for metallic minerals)
• Associated Minerals include quartz, nagyagite, calaverite, sylvanite, krennerite, pyrite and other sulfides.
• Other Characteristics: ductile, malleable and sectile, meaning it can be pounded into other shapes, stretched into a wire and cut into slices.
• Notable Occurrences include California and South Dakota, USA; Siberia, Russia; South Africa; Canada and other localities around the world.
• Best Field Indicators are color, density, hardness, sectility, malleability and ductility.