igneous

Snowflake Obsidian

Spherulitic Volcanic Glass (SiO2 + impurities)

Hardness: 5-5.5 (Mohs scale); Color: Black with white or grey 'snowflake' patterns; Luster: Vitreous (glassy); Crystal structure: Amorphous (non-crystalline) glass with crystalline inclusions; Specific gravity: 2.3-2.6.

Hardness: 5-5
Color: Black with white or grey 'snowflake' patterns
Luster: Vitreous (glassy)

Identified March 28, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the rapid cooling of felsic (silica-rich) lava. The 'snowflakes' are spherulites, which are radial clusters of needle-like cristobalite (a type of quartz) crystals that grew as the glass partially devitrified over time.

Uses & applications

Commonly used in jewelry (cabochons, beads), decorative carvings, and as a popular specimen for rock collectors. Historically, obsidian was used to make sharp cutting tools and blades.

Geological facts

Although it is an igneous rock, it is often called a 'mineraloid' because it lacks a true crystalline structure. The white patches represent the start of a transformation process where the volcanic glass begins to turn into different minerals.

Field identification & locations

Identify in the field by its smooth, glassy black base and conchoidal fracture, distinctively marked by white patches. Major deposits are found in volcanic regions of the United States (Utah, Oregon), Mexico, and Iceland.

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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)

mineral

Magnetite

Magnetite (Fe3O4)

mineral