igneous

Smoky Quartz in Matrix

Silicon dioxide (SiO2) within Pegmatite/Gneiss

Hardness: 7 (Mohs scale) for quartz; Color: Brown, smoky, translucent to opaque; Luster: Vitreous to greasy on crystal faces; Crystal Structure: Hexagonal (Trigonal); Cleavage: Indistinct/Conchoidal fracture; Specific Gravity: 2.65.

Hardness: 7 (Mohs scale) for quartz
Color: Brown, smoky, translucent to opaque
Luster: Vitreous to greasy on crystal faces

Identified April 6, 2026More igneous →

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Physical properties

Formation & geological history

Formed in late-stage cooling of magmatic pegmatites or in high-grade metamorphic environments. These crystals often grow within cavities or pockets of igneous rocks. The brown color is usually caused by natural gamma radiation activating aluminum impurities within the crystal structure.

Uses & applications

Commonly used as a decorative specimen for collectors, in landscaping, or processed into gemstones and beads for jewelry. When high-purity, quartz is used in electronics for its piezoelectric properties.

Geological facts

Smoky Quartz is the national gem of Scotland, where it is known as 'Cairngorm'. The dark color is unique because it is effectively a natural record of the rock's exposure to radiation over millions of years.

Field identification & locations

Identify by its ability to scratch glass and lack of cleavage. Look for the characteristic hexagonal prismatic points appearing from a host rock (matrix). Commonly found in mountainous regions with granitic outcrops like the Alps, Himalayas, or the Appalachian Mountains.

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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)

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Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

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Blue Apatite

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

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Magnetite

Magnetite (Fe3O4)

mineral