igneous

Pegmatite with Schorl (Black Tourmaline) and Mica

Pegmatite (complex association of NaAlSi3O8, NaFe3Al6(BO3)3Si6O18(OH)4, and KAl2(AlSi3O10)(OH,F)2)

Hardness: 6-7.5 (depending on mineral); Color: White/off-white matrix with black prismatic crystals and green/pink mica flakes; Luster: Vitreous to pearly; Crystal structure: Orthorhombic/Trigonal; Specific gravity: 2.6-3.2

Hardness: 6-7
Luster: Vitreous to pearly

Identified April 8, 2026More igneous →

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Physical properties

Formation & geological history

Formed during the final stages of a magma chamber's crystallization. The high water and volatile content allows for the growth of exceptionally large crystals in intrusive igneous environments.

Uses & applications

Used primarily as mineral specimens for collectors; granite-like varieties are used in construction, while specific minerals within (like tourmaline) may be used as gemstones if of high quality.

Geological facts

Pegmatites are known as 'nature's treasure chest' because they can contain giant crystals; some black tourmaline crystals in pegmatites have been recorded at several meters long.

Field identification & locations

Identify by finding very large, coarse-grained crystals embedded in a lighter feldspar or quartz matrix. Commonly found in mountainous regions with historical tectonic activity, such as the Appalachian or Rocky Mountains.

Other igneous specimens

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

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

Magnetite

Iron(II,III) oxide (Fe3O4)

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Blue Apatite

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

mineral

Magnetite

Magnetite (Fe3O4)

mineral