igneous

Pegmatite

Granitic Pegmatite

Hardness: 6.0-7.0 (average); Color: Mixed white, gray, beige, with black inclusions; Luster: Vitreous to pearly (mica); Crystal structure: Phaneritic (very large crystals); Cleavage: Perfect in mica flakes, poor in quartz.

Hardness: 6
Color: Mixed white, gray, beige, with black inclusions
Luster: Vitreous to pearly (mica)

Identified May 23, 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 melt allows crystals to grow to exceptional sizes, often in dikes or veins. Usually Precambrian to Cenozoic in age.

Uses & applications

Source of rare earth elements, lithium, gemstones (beryl, tourmaline), and industrial minerals like mica and feldspar. Used in high-end construction and electronics.

Geological facts

Pegmatites contains the largest crystals ever found on Earth, some reaching several meters in length. They are essentially 'giant-grained' granites.

Field identification & locations

Look for exceptionally large mineral grains (over 1cm) compared to surrounding rock. Commonly found in batholith margins. Identification relies on the presence of large plates of mica and blocky feldspar.

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