The most common schists are mica schists. Flakes of mica give them the
most marked schistosity, and a real shine. The flakes are typically about
O.5mmJO.02in thick and can often be prised off with a knife. There is
plenty of quartz in mica schist toO, often concentrated in mica-poor
layers, and a fair amount of albite feldspar. Sometimes red garnet or
green chlorite crystals are visible. The mica in mica schisrs can be
muscovite, sericite or biotite. Biotite is usually brown; muscovite and sericite
are pale coloured and called white mica. If a white mica is fine-grained,
it is called sericire; if it is coarser it is called muscovite. Most mica schists
contain all three, but one usually predominates. Muscovite and sericite
schists develop where metamorphism
The most common schists are mica schists. Flakes of mica give them the most marked schistosity, and a real shine. The flakes are typically about O.5mmJO.02in thick and can often be prised off with a knife. There is plenty of quartz in mica schist toO, often concentrated in mica-poor layers, and a fair amount of albite feldspar. Sometimes red garnet or green chlorite crystals are visible. The mica in mica schisrs can be muscovite, sericite or biotite. Biotite is usually brown; muscovite and sericite are pale coloured and called white mica. If a white mica is fine-grained, it is called sericire; if it is coarser it is called muscovite. Most mica schists contain all three, but one usually predominates. Muscovite and sericite schists develop where metamorphism
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