Benefactor robinjojo Posted June 19, 2022 · Benefactor Benefactor Share Posted June 19, 2022 (edited) The magnificent gold aurei, solidi, drachms, staters, escudos, soles and 20 dollar gold coins, to name a few, those coins whose images grace this website and auction catalogs all had their origins in the extraction of gold from in-situ, placer and lode deposits over the thousands of year that human kind sought, discovered and processed this coveted metal into coinage. The purpose of this thread is to provide a general guide of this different types of gold deposits that were exploited by empires, kingdoms and republics to enhance their economic status throughout the ancient and modern worlds. The photos illustrate the different forms that gold can take depending of the mode of deposit. Placer and lode alluvial surface deposits Gold, despite its softness, is an extremely durable native element. In sufficient concentrations, that is having relatively little associated quartz, massive water worn nuggets can be found on the the surface of deserts and plains where rivers used to flow eons ago, or in rivers or creeks. The alluvial gold deposits of ancient Lydia are an example of what is probably the first effort by human civilization to extract gold for the purpose for producing gold coinage. Gold nugget, Western Australia, 104.80 grams This specimen is basically solid gold. The surfaces are water worn, even though it was found in the vast desert of Western Australia. The surface display pits or cavities in which other minerals, mostly quartz weathered away. Gold nugget, Western Australia, 75.02 grams Gold found in alluvial deposits can vary in composition, as can be seen . Australia has produced nuggets that vary greatly in weight, with some weighing a kilo or more! Gold in quartz nugget, Western Australia, 120.56 grams Here, the nugget has a preponderance of quartz, which is a light tan color due to microscopic deposits of gold. Hard Rock (In-Situ) Deposits As civilizations developed, so did the techniques used to extract gold, notably through mining and refining ore. Here are some examples. Electrum, Seven Troughs Mining District, Fairview Mine, Pershing County, Nevada, 13.51 grams Native Gold, crystalline and quartz, Coulterville, California, 51.7 grams Native Gold, crystalline and quartz California 85.58 grams Native Gold, crystalline, with arsenopyrite and quartz Alleghany Co, California, 43.23 grams Native Gold in quartz with silver telluride Hessite (dark grey areas), Old Campbell Mine, Balmertown, Ontario, Canada, 43.5 grams In addition to quartz, gold is often associated with silver tellurides and pyrite. Native Gold, crystalline with quartz and pyrite, Turpin Mine, Gwanda, Zimbabwe, 21.71 grams The gold bearing ores that are more typically encountered show little, if any visual evidence of gold, even with normal hand magnification. The specimens shown are very rich examples. Here's a more typical example, and even this one is out of the ordinary. This a large piece of quartz with a very small spot of native gold visible. There might other minerals, including silver sulfide minerals. Do you see the gold? An old friend and retired school teacher owned a mine in the Sierra. When she passed away several years ago, her house, two doors down from mine, was the scene of chaos. Her nephew wanted the house emptied out quickly so it could be put on the market. The courtyard of the house was heaped with minerals that were ultimately destined for the landfill. I retrieved as many as I could, including this gold ore specimen, which I think came from the mine. Well, I hope this thread was informative. Gold really is where you find it, but it does comes in different forms. Edited June 19, 2022 by robinjojo 17 1 1 2 Quote Link to comment Share on other sites More sharing options...
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