New Mexico Mineral Symposium — Abstracts

To most gold seekers, gold prospecting means getting out the shovel, gold pan, sluice box, and plastic buckets, but this is not really gold mining. Placer mining is the recovery of gold after moth¬er nature has done the mining, milling, and concentrating of the heavy minerals, including gold. Yellow gold is only a small part of the gold story. The four faces of gold are the four ways gold exists, and all should be considered by any prospector seeking a productive venture into the world of gold.

Face one, crystalline gold—This face of gold is the most common form that weekend prospec¬tors seek. It includes flakes and nuggets of the yellow metal. Free gold is formed in a crystal pat¬tern (though often distorted by impact) and is identified by its crystalline lattice framework of gold molecules, orderly arrayed as the crystal grew naturally. Errant molecules of the other elements, such as silver, are commonly present. This is the gold of the Mother Lode, the Klondike of Canada, and of Breckenridge, Colorado.

Face two, refined gold or melted gold—This face of gold is represented by the fact that the gold is not crystalline but rather a solid solution or an alloy with other metals. This is the gold of jewel¬ry and coinage. Also, it is the gold of Fort Knox and the melted bubbles of gold that result from roasting the minerals of gold. The only difference between this face of gold and crystalline gold is that it is not naturally occurring and is a solid solution. The gold of Fort Knox is neither a solid solution nor an alloy; it is elemental gold (99.999% pure or 24K).

Face three, complex gold minerals—This face of gold is the gold of Cripple Creek and Boulder, Colorado, Romania, and the Carlin Trend of Nevada, and all of the other areas that produce refrac¬tory gold ore. These are the complex minerals of gold. Gold combines chemically as a compound and forms crystals with a lattice pattern. It differs profoundly from crystalline gold because the ele¬ments that comprise the anion in the mineral affect the structure of the crystal. This face of gold includes the tellurides and pyritic minerals such as pyrrhotite, arsenopyrite, marcasite, and pyrite often referred to as auriferous pyrite where molecules of gold are included in the crystal structure. The telluride minerals include sylvanite, krennerite, calaverite, muthmanite, nagyagite, etc.

Face four, the pseudomorphs of gold—This face of gold is present only in the supergene or oxi¬dized area of a rich telluride vein or orebody. It is residual gold that results from the leaching action of ground water in the process of erosion. Pseudomorphs of gold after sylvanite are known as "rusty gold," and after calavarite and krennerite are known as "mustard gold" or "sponge gold." These are the rarest forms of gold and are so rare that most people do not recognize them or know of their existence. They are not spectacular or beautiful like crystalline gold, in fact, they are somewhat ugly. The rareness stems from the fact that they exist only in the upper part (5-10 ft) of an oxidized telluride vein. They were the first gold to be sent to the smelter to put beans and bacon on a starving prospector's table. The pseudomorphs retain the lattice pattern of the original tel¬luride crystal but have voids that are left when ground water leaches away the tellurium. Thus, a porous and fragile framework of gold remains with no definite reflective crystal surface. The struc¬ture resembles rotten wood.

As with most things, the more you know about a subject, the more you realize how little you know. Knowledge provokes questions, and knowledge of gold is no exception.