Silver and its Ores
Bill Gallagher
ok to reproduce in entirety with credit.
Silver (Ag) is a native element precious metal that is very rarely found in pure form, being reactive with several common chemicals, most notably sulfur, and even with light itself. It is this latter attribute which was the basis of photography for over a century. In spite of this, silver is one of the most reflective of all materials, and it is also the greatest conductor of electricity and heat, among all the metals. Silver is a potent disinfectant and biocide, and it is thought that a certain class of people in Europe were once immune to some of the ravaging disease during medieval times due to ingesting minute amounts of silver, of which their eating utensils were made.
When found pure, one form of silver is called Wire Silver. Wire silver specimens command high prices, but not as high as the rare cube shaped or octahedral crystals. Massive silver has also been found, such as that from the Burro Mountains north of Silver City New Mexico, which was mined, loaded on train cars, and sent directly to a US Mint for melting into bullion and coins. This notation can be further researched in the book "Minerals of New Mexico" (ISBN: 082631662X/0-8263-1662-X)Northrop, Stuart A.; Labruzza, Florence A.
In pure form silver is usually found at the lower levels of lead, zinc or silver deposits. In most circumstances silver is a chemical component recovered from hard rock ore by a variety of refining processes which include smelting, electrolysis, and chemical leaching. The refinement of silver from ore nearly always includes pulverization of some sort, and the finer the grind the greater the recovery. Rocks containing silver are said to be Argentiferous. Many argentiferous rocks are found in the vicinity of manganese, and it is Psilomelane, a decorative-gem-form of botryoidal manganese, which the old time miners called "Cap of Silver". Almost all lead contains silver in nature, and it is actually the electrolytic De-silvering of natural lead which produces most of the worlds silver. Because of silvers photo-reactive properties, many of its ores and/or forms are black in color, and that color is of prime importance when searching for silver ore.
Other types of silver bearing materials: Argentite/Acanthite, technically Silver sulfide, is a psuedo-cubic crystalline form manifesting as dendrites, incrustations and masses. Chlorargyrite is Silver chloride, and forms as small grayish green crystals which turn purplish black or brown when exposed to light. Incidentally, any stone that darkens to blackish brown when exposed to light has a very good chance of containing silver. Polybasite is Silver copper antimony sulfide and forms as tabular somewhat hexagonal crystals with beveled edges which often exhibit triangular growth marks, or bladed or granular black masses. Pyrargyrite is Silver antimony sulfide and forms as hemimorphic prismatic reddish black crystals. Stephanite is also Silver antimony sulfide whose prismatic to tabular black crystals are rare, and the form is usually found massive or disseminated as coatings or layers in hydrothermically altered vugs. Proustite is Silver arsenic sulfide, which is usually shiny dark red and massive, though it may form striated rhombohedral crystals on occasion. Sylvanite is another form of silver ore, and is technically a Silver gold telluride which often forms as incrustations said to resemble writing, or as stubby prismatic and/or arborescent crystals.
For many years silver was the main stay of global coinage, and the American Dollars name is actually derived from a silver locale in Bohemia named Joachim or Joachimsthal, Thal = valley. The coins from this region were very popular in the world of commerce because of the size and purity. The coins became known as Joachimsthaler, and were minted all across Europe as a sort of standard. The name was changed or shortened in various venues, to Thaler, Taler, Daalder hence Dollar. The term two bits, which is synonymous with the American quarter dollar is said to be a reference to the Spanish version of this coin, the 8 reale silver piece, whose quarter measure was of course 2 reales, two bits of the 8.
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