igneous

Feldspar-rich Pegmatite

Granitic Pegmatite (principally KAlSi3O8)

Hardness: 6-6.5 (Mohs scale); Color: Pinkish-tan to brownish-orange; Luster: Vitreous to pearly; Crystal structure: Monoclinic/Triclinic; Cleavage: Two directions at nearly 90 degrees; Specific gravity: 2.5–2.6.

Hardness: 6-6
Color: Pinkish-tan to brownish-orange
Luster: Vitreous to pearly

Identified March 29, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow cooling of water-rich magma in the final stages of a granitic intrusion’s crystallization. This allows for the growth of very large crystals. These rocks can be found in terrains ranging from Precambrian to Cenozoic ages.

Uses & applications

Used in the manufacture of glass and ceramics (pottery, porcelain, tiles). It is also a source of semi-precious gemstones (such as moonstone or sunstone) and rare-earth minerals in larger deposits.

Geological facts

Feldspars make up about 60% of the Earth's crust. Granitic pegmatites are unique because they often contain rare elements like lithium, tantalum, and niobium which are not found in ordinary granite.

Field identification & locations

Identify in the field by its coarse crystal size (typically >1cm), blocky cleavage planes that reflect light, and typical pink/orange hue. Common in plutonic mountainous regions. Collectors look for well-formed crystal faces.

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

Blue Apatite

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

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Magnetite

Magnetite (Fe3O4)

mineral