Micas: Muscovite and BiotiteThe mica minerals have actually one perfect cleavage that enables them come be broken into an extremely thin sheets. This is really distinctive. Muscovite is clear, silvery, or coppery silver- in color (depending top top the thickness the the sample and presence the impurities) whereas new biotite is black. As soon as biotite weathers, the can become dark gold or coppery in color. Civilization have found golden flakes of weathering biotite in sand and, just like fool"s gold (pyrite), believed that this was real gold.
You are watching: The micas, biotite and muscovite, both exhibit one direction of cleavage
|This silvery clear color is properties of thin sheets that muscovite.|
|The large piece that muscovite has a silvery color, with darker coppery areas indicating a thick publication of muscovite sheets. |
Note the one square piece placed over the tongue of glass. It"s so clean it"s difficult to spot!
|On a black color background muscovite naturally appears darker, however the dark piece on the appropriate is virtually this dark top top a white background because of the thickness.|
|No matter just how dark muscovite gets, new biotite is patent darker.These sheets the biotite are as thin together in the very first muscovite photograph above, but they room black and shiny, no silvery and shiny.|
|This big book that biotite (~ 6" across) reflects the 6-sided shape of perfect biotite crystals. Over there is a smaller publication to the left.It is easy to peel off thin black sheets of black color biotite to produce a pile as in the photo above.The white mineral is calcite, i m sorry is not frequently found through biotite.|
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