igneous

Garnetiferous Pegmatite

Pegmatite with Almandine Garnet and Muscovite

Hardness: 6.5-7.5 (garnets) 6 (feldspar); Color: White to grey matrix with red/pink garnet inclusions; Luster: Vitreous to pearly; Crystal structure: Course-grained igneous; Cleavage: Perfect in mica, poor in garnet.

Hardness: 6
Color: White to grey matrix with red/pink garnet inclusions
Luster: Vitreous to pearly

Identified May 7, 2026More igneous →

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Physical properties

Formation & geological history

Formed during the final stages of a magma's crystallization, usually in high-water content environments that allow for very large crystal growth. Typical of continental crust and orogenic belts.

Uses & applications

Used as a source of rare minerals, industrial abrasives (garnet), and sometimes as decorative stone or countertop material. High-quality garnets are used in jewelry.

Geological facts

Pegmatites are famous for containing the largest crystals of any rock type. The red spots are likely almandine garnets, which are common in metamorphic and igneous rocks.

Field identification & locations

Identify by looking for unusually large mineral grains (over 1cm) and the presence of deep red, dodecahedral garnet crystals. Common in pegmatite veins globally, such as in the Northeast US or Brazil.

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