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Pyroxene (Diopside)

The Silicate Minerals

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Pyroxenes are important in dark igneous rocks and are second to olivine in the Earth's mantle. Learn more about the pyroxenes. This is diopside. (more below)
Mixed metal silicates
Photo courtesy Maggie Corley of Flickr.com under Creative Commons License
Pyroxenes are so common that together they are considered rock-forming minerals. You can pronounce pyroxene "PEER-ix-ene" or "PIE-rox-ene," but the first tends to be American and the second British. Diopside has the formula CaMgSi2O6. The Si2O6 part signifies chains of silicon atoms bound together with oxygen atoms; the other atoms are arranged around the chains. The crystal form tends to be short prisms, and cleavage fragments have a nearly square cross section like this example. That is the main way to distinguish a pyroxene from the amphiboles (which have a lozenge-shaped cross section).

Other important pyroxenes include augite, the enstatite-hypersthene series and aegirine in igneous rocks; omphacite and jadeite in metamorphic rocks; and the lithium mineral spodumene in pegmatites. See them and more in the Pyroxene Gallery.

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