Chalcopyrite Facts

Chalcopyrite Facts
Described as the world's most important ore of copper for nearly five thousand years is chalcopyrite. Some chalcopyrite has enough gold or silver that it can be an ore of those metals without the consideration of its copper content. Chalcopyrite is found in most sulfide mineral deposits throughout the world, which is its chemical classification. Its color can be brownish yellow but tarnishes to gray green and can sometimes be iridescent. The streak is greenish black, opaque, with a metallic luster, and poor cleavage. On the Mohs Hardness scale, it scores between 3.5 and 4.0, a specific gravity between 4.1 and 4.3, with a tetragonal crystal system. Its diagnostic properties include its color, streak, and it is softer than pyrite and brittle.
Interesting Chalcopyrite Facts:
Upon weathering, the surface of chalcopyrite loses its metallic luster and brass-yellow becoming a dull gray-green color, but in the presence of acids, the tarnish can develop red to blue to purple iridescence.
The weathered chalcopyrite attracts attention and some mineral shops will sell it as "peacock ore", which is actually bornite.
Chalcopyrite has a similar appearance as pyrite and gold, but distinguishing the difference is easy. Gold is softer and has a yellow streak. Pyrite cannot be scratched with a nail, but chalcopyrite can be easily scratched.
Chalcopyrite is also given the name "fool's gold", along with pyrite, because of its similar appearance, though it is not as common as pyrite.
The mineral forms under several different conditions, including primary, crystallizing from melts as accessory minerals in igneous rocks.
Some chalcopyrite forms by magmatic segregation in stratified rocks of a magma chamber, and some may occur in pegmatite dikes and contact metamorphic rocks.
Others may be disseminated through schist and gneiss, and many volcanogenic massive sulfide deposits contain chalcopyrite.
Chalcopyrite deposits mined that are hydrothermal in origin are the most significant, with some of the mineral occurring in veins and some replacing country rock.
The minerals commonly associated with chalcopyrite include pyrite, bornite, chalcocite, galena, and sphalerite.
Removing chalcopyrite from secondary mineral deposits resulting in copper can be done by weathering or solution, transported a short distance, and then redeposited as secondary oxide, sulfide, or carbonate minerals.
The most important use of chalcopyrite is as an iron ore of copper, and has been since smelting began five thousand years ago. Some chalcopyrite ores have significant amounts of zinc substituting for iron.
Chalcopyrite is a common mineral and can be found all over the world in many places. In the United States, important mining of the mineral has occurred in Kansas, Oklahoma, and Missouri.
In Pennsylvania, the production of large highly tarnished and distorted crystals are often sought by mineral collectors.

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