igneous

Quartz crystals on Basalt

SiO2 (Quartz) on Mafic Igneous Rock (Basalt)

Hardness: 7 (Quartz), 5-6 (Basalt host); Color: Colorless to white crystals on a dark grey/black matrix; Luster: Vitreous (crystals) to dull (host); Crystal Structure: Hexagonal/Trigonal; Cleavage: None (conchoidal fracture)

Hardness: 7 (Quartz), 5-6 (Basalt host)
Color: Colorless to white crystals on a dark grey/black matrix
Luster: Vitreous (crystals) to dull (host)

Identified May 27, 2026More igneous →

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Physical properties

Formation & geological history

Formed via hydrothermal precipitation where silica-rich fluids filled vesicles or cracks in basaltic lava flows. The basalt formed from cooling lava, while the quartz crystals grew later as mineral-rich water permeated the rock.

Uses & applications

Geological collecting, educational specimens, and small-scale ornamental pieces. Basalt itself is heavily used in construction as aggregate.

Geological facts

Basalt is the most common volcanic rock on Earth and makes up most of the ocean floor. Small quartz druses like this are frequently found in gas bubbles known as amygdules.

Field identification & locations

Identified by the contrast between the dark, fine-grained host rock and the hard, glassy crystals that can scratch glass. Common in volcanic terrains such as the Pacific Northwest, India (Deccan Traps), or Iceland.

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

Dalmatian Jasper

Aplite with Arfvedsonite inclusions

igneous

Magnetite

Iron(II,III) oxide (Fe3O4)

mineral

Blue Apatite

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

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

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