igneous
Pegmatite (Quartz, Feldspar, and Tourmaline/Biotite)
Pegmatitic Igneous Rock
Hardness ranges from 6 to 7 on the Mohs scale depending on the mineral component (quartz vs. feldspar). Colors include milky white, pink, and dark black/brown. The luster is vitreous to pearly, with interlocking coarse-grained crystals.
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Physical properties
Hardness ranges from 6 to 7 on the Mohs scale depending on the mineral component (quartz vs. feldspar). Colors include milky white, pink, and dark black/brown. The luster is vitreous to pearly, with interlocking coarse-grained crystals.
Formation & geological history
Formed from the cooling of magma rich in volatile elements deep within the Earth's crust, allowing exceptionally large crystals to grow. Geological age varies widely depending on the specific intrusion.
Uses & applications
Source of industrial minerals, rare earth elements, gemstone mining, and geological specimens for collectors.
Geological facts
Pegmatites are famous for containing some of the largest individual crystals ever found on Earth, sometimes measuring many meters in length.
Field identification & locations
Easily identified by its extremely coarse, interlocking crystal texture (phaneritic) containing distinct patches of clear/white quartz, pink potassium feldspar, and dark accessory minerals. Found worldwide in ancient cratons and mountain-building belts.
