why is gold often found in veins of quartz

Igneous Igneous rock (derived from the Latin word "Igneous" meaning of fire, from "Ignis" meaning fire) is one of the three main rock types (the others being se
dimentary and metamorphic rock). Igneous rock is formed by magma or lava (molten rock) cooling and becoming solid. Igneous rock may form with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. This magma can be derived from partial melts of pre-existing rocks in either a planet's mantle or crust. Typically, the melting is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition. Over 700 types of igneous rocks have been described, most of them having formed beneath the surface of Earth's crust. These have diverse properties, depending on their composition and how they were formed. rock (derived from the Latin word "Igneus" meaning of fire, from "Ignis" meaning fire) is one of the three main rock types (the others being sedimentary and metamorphic rock).


Igneous rock is formed by magma or lava (molten rock) cooling and becoming solid. Igneous rock may form with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. This magma can be derived from partial melts of pre-existing rocks in either a planet's mantle or crust. Typically, the melting is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition. Over 700 types of igneous rocks have been described, most of them having formed beneath the surface of Earth's crust. These have diverse properties, depending on their composition and how they were formed. Gold and silver are obtained from a variety of ores. Most people think of nuggets and such, but the truth is that very little comes from nuggets - nearly all newly mined gold comes from ores mined from the natural hard rocks that contain gold in tiny, even microscopic particles.


This webpage is created to show what some of those ores look like. Gold is found widely diffused in nature even though it is one of the scarcer metals. Very commonly, gold occurs as the native metal encased within quartz. Sometimes the gold is in a finely divided state, sometimes in particles of considerable size, as nuggets, grains, scales, plates, threads and wires in quartz rock. It occurs also in a finely divided state disseminated through schistose rocks, slates and some sedimentary rocks like limestone. In these cases the rock has been altered by the flow of heated and mineralized waters, often resulting in the impregnation of large amounts of rock with silica and iron. Sometimes the silicified rock even replaces the original country rock. While historically speaking vein deposits were the most productive, these disseminated deposits currently yield much of the worlds gold ore.


Within gold ores, the element occurs in nature chiefly as native gold, which is by far the most common gold bearing mineral. In various gold ores, the native gold commonly occurs as tiny particles contained within sulfide minerals such as pyrite. Iron pyrite is an exceedingly common associate with gold, but it also serves as a reducing agent. Therefore whenever gold is found encased in pyrite, it is always present as free gold and not as some type of gold sulphide. Gold is also found at times in chalcopyrite, galena and and, but not as a rule in such large amounts as may be found in pyrite. Other minerals, like, pyrrhotite, and sometimes carry small amounts of gold as well. Gold also occurs as tellurides such as calaverite. Common gangue minerals in gold ores include quartz, and pyrite, but many others can be found in smaller amounts.

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