igneous

Granitic Pegmatite with Schorl

Granitic Pegmatite (Schorl: NaFe3Al6(Si6O18)(BO3)3(OH)3OH)

Hardness: 6-7.5 (Mohs scale); Color: White matrix (quartz/feldspar) with black inclusions (tourmaline/schorl); Luster: Vitreous to pearly; Crystal structure: Trigonal/Hexagonal; Cleavage: None/Conchoidal.

Hardness: 6-7
Luster: Vitreous to pearly

Identified March 4, 2026More igneous →

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Physical properties

Formation & geological history

Formed during the final stages of a magma's crystallization, where high water content allows for the growth of extremely large crystals. Typical of Proterozoic to Phanerozoic granitic intrusions.

Uses & applications

Primarily used as a source for rare elements like lithium, tantalum, and gemstones. Common specimens are used for educational purposes or architectural surfaces.

Geological facts

Pegmatites are known for containing some of the largest individual crystals ever discovered, sometimes over 10 meters long. The black inclusions are likely Schorl, the most common member of the tourmaline group.

Field identification & locations

Identify by its 'giant' grain size compared to regular granite. Usually found in mountainous regions or shield areas. Collectors should look for distinct geometric patterns and accessory minerals with vitreous luster.

Other igneous specimens

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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)

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

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Blue Apatite

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

mineral

Magnetite

Magnetite (Fe3O4)

mineral