A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than 1 cm (0.4 in) and sometimes greater than 1 meter (3 ft). Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic composition to granite. However, rarer intermediate composition and mafic pegmatites are known.
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
Igneous rock, or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava.
Geologic provinces of the world (USGS) Shield Platform Orogen Basin Large igneous province Extended crust Oceanic crust: 0–20 Ma 20–65 Ma >65 Ma
Volcanic eruptions of lava are major sources of igneous rocks. (Mayon volcano in the Philippines, erupting in 2009)
Natural columns of igneous rock separated from each other by columnar joints, in Madeira
Formation of igneous rock
