Moon Metal
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Moon Metal
of Genesis mentions silver as part of Abraham's treasure. Chinese and Persian references speak of silver by about 2500 B.C. By this time, mining may have begun, with workers extracting silver ore as well as coAccording to ancient records, silver was incidentaUy melted lumps of pure metal. the third metal used by man, after gold and copper. Pure silver is sometimes found in The Romans developed the first extenlarge lumps, so it could be used without sive mining and smelting operations, uscomplex refinement and separation procing large furnaces to produce silver metal esses. from ore. Pliny wrote that "the ore was washed and sieved five times, fused with Initially, most of silver's value lay in its malleability, lustrous white color, resist- lead and then cupelled for more silver." Cuance to corrosion (which allowed it to re- pellation, the process of heating ore to high temperatures under a blast of air, oxidizes main shiny even after being buried for a the lead to more volatile lead oxide, which long time), and resistance to atmospheric burns off. oxidation. But in the 20th century, silver's high thermal and electrical conductivity, as The Roman process was used throughwell as its corrosion resistance, make it an out the Middle Ages until the 16th century, attractive material for many high-tech when Spanish discoveries of enormous uses. lodes of silver in the Americas led to the development of new techniques. Silver ore Silver, one of the so-called "precious found in Mexico, Bolivia, and Peru was metals," is the whitest of all metals, and its reflectivity (especially in the portion of the richer in silver than European ores. New World Spanish metallurgists ground the spectrum visible to the human eye) is one of the highest among metals. Polished sil- ore with water into a mud, mixed it with ver can reflect up to 95% of the light strik- salt, and added roasted sulfide ores of copper and iron and some mercury. Mules ing its surface. It has excellent ductility and trod on this mud for several days on a malleability, though it can be easily paved court, reducing the silver to metal scratched. With the clean air of pre-industrial soci- and creating an amalgamation with the mercury. The amalgam was then collected, eties, tarnishing was not a problem, but silver reacts with sulfur compounds in the retorted, and sent to a refinery for cupellaatmosphere (brought about by large-scale tion. This process continued to be used for burning of coal). Now, silver must be the next three centuries. coated with nickel and then rhodium, or The next refining advancement did not alloyed with palladium or gold to keep it occur until 1802, when D'Arcet in Paris defrom discoloring. Silver objects found in veloped the sulfuric acid process. Most ancient tombs were initially bright even silver-bearing ores contain a small amount over the ages, but they tarnish rapidly on of gold, which cupellation cannot remove. contacting modern polluted air. However, D'Arcet discovered that dissolvThe ancients compared the yellow color ing crude
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