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Arsenopyrite

earth science Maturity 7-9 Next article →

Arsenopyrite is a very special kind of mineral. It is a hard, metallic substance. It looks like steel grey or silver white. This mineral is quite heavy for its size. It is made of iron, arsenic, and sulfur.

People use it to find arsenic. Arsenic is a chemical element found in this ore. It has an arsenic content of 46 percent. This makes it a principal ore for that element.

Arsenopyrite by petrographic microscope NL
Arsenopyrite by petrographic microscope NL

There are many ways to see how it works. If you heat the mineral, it makes a vapor. This vapor is made of arsenic and sulfur. You can also use nitric acid on it. The acid makes the mineral release elemental sulfur. When the mineral touches the air, it changes. It slowly turns into iron arsenates. This happens when deposits are exposed to the atmosphere.

People have used different names for this mineral. Older books call it mispickel. That name comes from the German language. Some people also call it mundic. That word comes from a Cornish dialect. It is often found near gold. Miners use it to find gold bearing reefs. This is because it can be associated with gold.

Arsenopyrite by petrographic microscope NL
Arsenopyrite by petrographic microscope NL

Scientists study the way the mineral grows. It belongs to the monoclinic crystal system. This describes how the tiny parts are arranged. It often forms long, column shapes. These shapes are called prismatic crystals. The crystals can also show twinning. They may also have lines called striations. Each iron center links to three arsenic atoms. It also links to three sulfur atoms.

This mineral is very useful for learning about science. It is found in high temperature hydrothermal veins. It can also be in pegmatites. You might find it in areas of contact metamorphism. Some gold in this mineral is refractory. This means the gold is hard to reach. It is not easily leached with cyanide. This makes the gold hard to get out.

Arsenopyrite by petrographic microscope NL
Arsenopyrite by petrographic microscope NL
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File:Arsenopyrite by petrographic microscope NL.jpg
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