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Ferromagnesian Silicates

In detail, how do olivine, pyroxene, amphibole, and biotite differ?

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1. In detail, how do olivine, pyroxene, amphibole, and biotite differ?

Let's look at each to help you see the differences.

OLIVINE

? Olivine is common only in ultramafic igneous rocks like dunite and peridotite.
? It occurs as small, light green, glassy crystals (see image to the left at this source).
? It has no cleavage.
? The texture of olivine in igneous rocks is often termed sugary. Run your fingers over the grains, do they feel like sandpaper? The mineral is most probably olivine.
? Although olivine occurs in gabbro and basalt, it is far more common in peridotite and dunite. Because of the light green color and sugary texture it is rarely confuded with other rock-forming minerals. (http://geology.csupomona.edu/alert/igneous/igmin.htm)

PYROXENE

? Pyroxene is common only in mafic igneous rocks.
? It occurs as short, stubby, dark green crystals (see image to the left at the source listed below).
? It has poor cleavage in 2 directions ...

Solution Summary

In detail, this solution identifies and explains how olivine, pyroxene, amphibole, and biotite differ. References are provided.

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