igneous
Pegmatite
Igneous Pegmatite (Quartz-Feldspar-Mica)
Hardness: 6-7 on the Mohs scale; Color: Varies, commonly white, grey, pink, or multicolored due to feldspar and quartz; Luster: Vitreous to pearly; Crystal structure: Very coarse-grained phaneritic, often with giant crystals; Cleavage: Good in feldspar, none in quartz; Specific Gravity: 2.5-2.8
- Hardness
- 6-7 on the Mohs scale
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-7 on the Mohs scale; Color: Varies, commonly white, grey, pink, or multicolored due to feldspar and quartz; Luster: Vitreous to pearly; Crystal structure: Very coarse-grained phaneritic, often with giant crystals; Cleavage: Good in feldspar, none in quartz; Specific Gravity: 2.5-2.8
Formation & geological history
Formed from the water-rich, late-stage crystallization of magma cooling slowly deep within the Earth's crust, often containing rare elements.
Uses & applications
Source of industrial minerals like feldspar and mica, rare earth elements, gemstone mining (such as tourmaline, beryl, and topaz), and specimen collecting.
Geological facts
Pegmatites can host some of the largest individual crystals ever found on Earth, sometimes measuring several meters in length.
Field identification & locations
Identified by its extremely coarse, interlocking crystal texture (often significantly larger than surrounding granitic rocks) containing visible quartz, feldspar, and mica flakes. Found globally in ancient cratons and mountain-building belts.
