igneous

Granite Pegmatite with Muscovite Mica

Granite Pegmatite (Silicon Dioxide and complex silicates)

Hardness: 6-7 (Quartz/Feldspar) and 2-2.5 (Mica); Color: White, cream, and silver-grey; Luster: Vitreous to Pearly; Crystal structure: Coarse-grained phaneritic; Cleavage: Perfect basal in mica flakes.

Hardness: 6-7 (Quartz/Feldspar) and 2-2
Color: White, cream, and silver-grey
Luster: Vitreous to Pearly

Identified June 2, 2026More igneous →

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Physical properties

Formation & geological history

Formed during the final stages of a magma's crystallization. Highly fluid, water-rich melts allow for the growth of large crystals in intrusive environments. Commonly found in batholiths and orogenic belts.

Uses & applications

Source of industrial minerals like mica (insulation, cosmetics), quartz (electronics), and feldspar (ceramics). Also collected as geological specimens.

Geological facts

Pegmatites often contain rare earth elements and some of the largest individual crystals ever recorded. The sparkly silver flakes are Muscovite, often called 'Isinglass' and were historically used as heat-resistant window material.

Field identification & locations

Identify by exceptionally large crystal size compared to surrounding rock and the presence of 'books' or flakes of shiny mica that can be peeled with a fingernail. Found in mountainous or crystalline basement regions.

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Granite

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Granite

Igneous

Blue Apatite

Fluorapatite (Ca5(PO4)3F)

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Dalmatian Jasper

Aplite with Arfvedsonite inclusions

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Magnetite

Iron(II,III) oxide (Fe3O4)

mineral

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