igneous

Basalt with Magnetite inclusions

Basalt (Mafic silicate rock) potentially containing Magnetite (Fe3O4)

Hardness: 6 (Mohs scale); Color: Dark grey to black with metallic silver flecks; Luster: Sub-metallic to dull; Structure: Fine-grained (aphanitic); Specific Gravity: 3.0

Hardness: 6 (Mohs scale)
Color: Dark grey to black with metallic silver flecks
Luster: Sub-metallic to dull

Identified March 22, 2026More igneous →

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Physical properties

Hardness: 6 (Mohs scale); Color: Dark grey to black with metallic silver flecks; Luster: Sub-metallic to dull; Structure: Fine-grained (aphanitic); Specific Gravity: 3.0

Formation & geological history

Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the surface of a terrestrial planet or the moon. Most specimens date from the Cenozoic era or are found in active volcanic zones.

Uses & applications

Used primarily in construction (crushed stone, concrete aggregate) and road base. Magnetite-rich varieties are studied for paleomagnetism and industrial iron extraction.

Geological facts

Basalt is the most common rock type in the Earth's crust, making up most of the ocean floor. When it contains significant magnetite, it can actually deflect a compass needle.

Field identification & locations

Identify in the field by its dark color, heavy weight (density), and fine-grained texture. Use a strong magnet to see if it exhibits magnetic attraction, common in dark volcanic specimens. Found globally in volcanic regions like Iceland, Hawaii, and the Pacific Northwest.

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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

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