Igneous

Basalt (with possible mineral veining)

Basalt (Aphanitic Mafic Igneous Rock)

Hardness: 6-7 (Mohs scale); Color: Dark grey to black, occasionally weathered to brown; Luster: Dull/Earthy; Crystal structure: Aphanitic (fine-grained); Cleavage: None; Specific Gravity: 2.8-3.0.

Hardness: 6-7 (Mohs scale)
Color: Dark grey to black, occasionally weathered to brown
Luster: Dull/Earthy

Identified March 26, 2026More igneous →

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Physical properties

Hardness: 6-7 (Mohs scale); Color: Dark grey to black, occasionally weathered to brown; Luster: Dull/Earthy; Crystal structure: Aphanitic (fine-grained); Cleavage: None; Specific Gravity: 2.8-3.0.

Formation & geological history

Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. This specimen shows signs of fluvial or glacial rounding, indicating it was transported by water or ice over a long period.

Uses & applications

Commonly used as an aggregate in construction (road base, concrete, railroad ballast), for stone carvings, and occasionally in jewelry as or healing stones when polished.

Geological facts

Basalt is the most common rock type on Earth's crust and makes up most of the ocean floor. It is also found extensively on the Moon and Mars.

Field identification & locations

Identify in the field by its dark color, heavy weight (density), and fine-grained texture. To distinguish from slate, check for a lack of foliation. Commonly found in volcanic fields, ocean basins, and riverbeds.

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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)

mineral

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