igneous

Granitic Pegmatite

Pegmatite containing Quartz, Feldspar, and Muscovite mica

Hardness: 6-7 (quartz/feldspar) and 2-2.5 (mica). Color: White, cream, smoky, and silver. Luster: Vitreous to pearly. Crystal structure: Large, interlocking phaneritic crystals. Cleavage: Perfect in mica, distinct in feldspar.

Hardness: 6-7 (quartz/feldspar) and 2-2
Color: White, cream, smoky, and silver
Luster: Vitreous to pearly

Identified May 23, 2026More igneous →

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Physical properties

Formation & geological history

Formed during the final stage of a magma's crystallization. Highly water-enriched residual fluids allow for the rapid growth of exceptionally large crystals, typically in intrusive dikes or veins.

Uses & applications

Major source of rare elements (lithium, tantalum) and industrial minerals like mica and quartz. Used in high-end construction slabs and as a source for gemstone-quality minerals.

Geological facts

Pegmatites are famous for holding the record for the largest individual crystals ever found on Earth, including spodumene crystals over 40 feet long.

Field identification & locations

Identified by the extremely large grain size compared to surrounding rock. Look for shiny, flaky mica books and glassy quartz masses in mountain belts and shield areas.

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

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Dark Igneous Rock (Likely Basalt or Diabase)

Basalt (extrusive igneous rock) or Diabase (intrusive igneous rock - also known as Dolerite), largely composed of plagioclase feldspar, pyroxene (augite), and sometimes olivine and amphibole. Exact mineralogy would require thin section analysis.

Igneous

Magnetite

Iron(II,III) oxide (Fe3O4)

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Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

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Blue Apatite

Apatite (Group), Ca5(PO4)3(F,Cl,OH)

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Magnetite

Magnetite (Fe3O4)

mineral