详情
Gold ore 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 arsenopyrite and stibnite, but not as a
rule in such large amounts as may be found in pyrite. Other
minerals, like sphalerite, pyrrhotite, magnetite and hematite
sometimes carry small amounts of gold as well. Gold also occurs as
tellurides such as calaverite. Common gangue minerals in gold ores
include quartz, fluorite, calcite and pyrite, but many others can
be found in smaller amounts.
