Granite
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Granite is a coarse-grained intrusive igneous rock composed mostly of quartz, alkali feldspar, mica and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slow
Granite containing plagioclase feldspar, potassium feldspar, quartz, biotite, and/or amphibole
Granite with a moderate amount of plagioclase, alkali feldspar, and quartz
Granite with a composition of alkali feldspar and quartz
Granite in thin section, under cross-polarized light
Pegmatite
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A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than 1 cm and sometimes greater than 1 meter. Most pegmatites are composed of qua
Pegmatite with blue corundum crystals
Pegmatite containing lepidolite, tourmaline, and quartz from the White Elephant Mine in the Black Hills, South Dakota
Proterozoic pegmatite swarm in the headwall of the cirque of a small mountain glacier, northeastern Baffin Island, Nunavut
Rose muscovite from the Harding Pegmatite Mine