igneous

Rough Quartz in Pegmatite Matrix

Quartz (Silicon Dioxide - SiO2) in Granitic Pegmatite

Hardness: 7 (Mohs scale), Color: Dirty white to light tan with reddish-brown iron staining, Luster: Vitreous to dull, Crystal structure: Trigonal/Hexagonal, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Identified March 24, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow cooling of magma deep underground, specifically in pegmatites where large crystals have room to grow. Geological age can range from hundreds of millions to billions of years depending on the host formation.

Uses & applications

Used primarily as aggregate in construction or as a source of silica for glassmaking and electronics (semiconductors). Low-grade rough specimens are often kept for amateur rock collections.

Geological facts

Quartz is the second most abundant mineral in Earth's continental crust. Specimens with reddish staining often get their color from secondary iron oxide infusions (limonite or hematite) that seep into microscopic fractures.

Field identification & locations

Identify in the field by its hardness (it can scratch glass), lack of cleavage, and translucent nature. It is extremely common in mountainous regions with granitic outcrops. Collectors should look for translucency on broken edges.

Other igneous specimens

See all

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