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While the majority of quartz crystallizes from molten magma, quartz also chemically precipitates from hot hydrothermal veins as gangue, sometimes with ore minerals like gold, silver and copper. Large crystals of quartz are found in magmatic pegmatites. [22] Well-formed crystals may reach several meters in length and weigh hundreds of kilograms ...
In the spring of 1859, after digging down to a depth of about ten feet, they found a gold-rich reddish quartz vein. Their discovery was actually part of the Comstock Lode, the Old Red Ledge. [2]: 5–6 The four men are therefore credited with the rediscovery of the mine previously found by the Grosh brothers. [5]
Silver is found in the Earth's crust in the pure, free elemental form ("native silver"), as an alloy with gold and other metals, and in minerals such as argentite and chlorargyrite. Most silver is produced as a byproduct of copper, gold, lead, and zinc refining. Silver has long been valued as a precious metal.
It is also found in association with sphalerite in low-temperature lead-zinc deposits within limestone beds. Minor amounts are found in contact metamorphic zones, in pegmatites, and disseminated in sedimentary rock. [8] In some deposits, the galena contains up to 0.5% silver, a byproduct that far surpasses the main lead ore in revenue. [9]
[5] [6] Various amalgams of silver and mercury or other metals and mercury do occur rarely as minerals in nature. An example is the mineral eugenite (Ag 11 Hg 2) and related forms. [7] Silver nuggets, wires, and grains are relatively common, but there are also a large number of silver compound minerals owing to silver being more reactive than gold.
In 1986, California named benitoite as its state gemstone, a form of the mineral barium titanium silicate that is unique to the Golden State and only found in gem quality in San Benito County. [ 80 ] ^ Colorado is the only state whose geological symbols reflect the national flag's colors: red (rhodochrosite), white (yule marble), and blue ...
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Pyrite is usually found associated with other sulfides or oxides in quartz veins, sedimentary rock, and metamorphic rock, as well as in coal beds and as a replacement mineral in fossils, but has also been identified in the sclerites of scaly-foot gastropods. [14]