igneous
Granite Pegmatite with Tourmaline and Muscovite
Pegmatite (Feldspar: KAlSi3O8, Quartz: SiO2, Schorl: NaFe2+3Al6(Si6O18)(BO3)3(OH)3(OH))
Hardness: 6-7.5 (depending on mineral); Color: White to light grey matrix with black crystals; Luster: Vitreous to pearly; Structure: Macro-crystalline phaneritic; Cleavage: Perfect on mica, poor on quartz.
- Hardness
- 6-7
- Color
- White to light grey matrix with black crystals
- Luster
- Vitreous to pearly
Identified More igneous →
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Physical properties
Hardness: 6-7.5 (depending on mineral); Color: White to light grey matrix with black crystals; Luster: Vitreous to pearly; Structure: Macro-crystalline phaneritic; Cleavage: Perfect on mica, poor on quartz.
Formation & geological history
Formed during the final stages of a magma's crystallization. Highly fluid, water-rich melts allow for the growth of exceptionally large crystals in intrusive igneous environments.
Uses & applications
Used in gemstone collection, mineral specimens for education, and industrial sources of rare elements like lithium, beryllium, and high-purity quartz/mica.
Geological facts
Pegmatites are famous for containing some of the largest crystals on Earth, sometimes reaching over 10 meters in length. This specimen specifically shows black schorl tourmaline embedded in a quartz-feldspar matrix.
Field identification & locations
Identify in the field by looking for unusually large grain sizes compared to surrounding granite. Found globally in continental shields like Brazil, Madagascar, and the Appalachian Mountains.
