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High-grade gold ore from the Harvard Mine, Jamestown, California, a wide quartz-gold vein in California's Mother Lode.Specimen is 3.2 cm (1.3 in) wide. Various theories of ore genesis explain how the various types of mineral deposits form within Earth's crust.
Gold exists in several forms in the Earth's surface environment including Au(I/III)-complexes, nanoparticles, and placer gold particles (nuggets and grains). The gold biogeochemical cycle is highly complex and strongly intertwined with cycling of other metals including silver, copper, iron, manganese, arsenic, and mercury. [ 2 ]
Neolithic Age (new stone era) beginning about 10,200 years ago: flint tools (diagenesis of marine microfossils, microcristalline opal and chalcedony), jade tools (usually nephrite, jadeitite or jadeite-jade is less common), kaolin earth (adobe bricks made by drying of clay), copper, gold, silver and rocksalt.
Most minerals on Earth formed after photosynthesis by cyanobacteria (pictured) began adding oxygen to the atmosphere. Mineral evolution is a recent hypothesis that provides historical context to mineralogy. It postulates that mineralogy on planets and moons becomes increasingly complex as a result of changes in the physical, chemical and ...
A variety of gold deposits are formed in accretionary orogens, including orogenic gold deposits. [38] Orogenic gold deposits are typically located in metamorphosed fore-arc and back-arc regions, as well as in the arc [3] and show a close spatial relationship to lamprophyres and associated felsic porphyry dikes and sills. [39]
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Gold, a chemical element; Genomes OnLine Database; Global-scale Observations of the Limb and Disk, a NASA Explorer Mission of Opportunity; GOLD (parser), an open-source parser-generator of BNF-based grammars; Graduates of the Last Decade, an Institute of Electrical and Electronics Engineers program to garner more university level student members
These deposits are formed by hot, mineral-rich fluids that circulate through fractures and cracks in rocks. As the fluids cool, they deposit minerals, such as gold, silver, copper, lead, and zinc, into the veins. [2] EVP are typically small in size, but they can be very high-grade, meaning that they contain a high concentration of valuable ...