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Biotite granite thin section exhibiting abundant biotite crystals within a typical granite crystal mass. These thin sections supplement the hand specimens nicely and allow the crystallisation history of the rock to be interpreted.
Biotite granite is a coarse grained, felsic intrusive igneous rock, the minerals which make up a granite are typically quartz, feldspars and micas. In the case of biotite granite, the constituent minerals are milky (white) quartz, plagioclase feldspar which is often white and biotite mica crystals. These thin sections show this well; the green, brown or tanned colours of the biotite stand proudly among the colourless quartz and feldspar crystals in PPL view. Likewise in XPL view the high 3rd and 4th order interference colours allow the biotite to stand out prominently; the strong mineral colour may mask this slightly however. The material from which these thin sections were cut was collected from Scotland, UK. Each section is made to 30 microns thickness. The glass is 46 x 27 mm in size, supplied in a protective card sleeve with a label, ideal for microscopy.
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