Igneous

Basalt (Vesicular)

Mafic Volcanic Rock (rich in Magnesium and Iron)

Hardness: 5-6 (Mohs scale); Color: Dark grey, black, or reddish-brown due to oxidation; Luster: Dull/Earthy; Structure: Fine-grained aphanitic with small pits (vesicles); Specific Gravity: 2.8-3.0.

Hardness: 5-6 (Mohs scale)
Color: Dark grey, black, or reddish-brown due to oxidation
Luster: Dull/Earthy

Identified March 21, 2026More igneous →

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Physical properties

Hardness: 5-6 (Mohs scale); Color: Dark grey, black, or reddish-brown due to oxidation; Luster: Dull/Earthy; Structure: Fine-grained aphanitic with small pits (vesicles); Specific Gravity: 2.8-3.0.

Formation & geological history

Formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near a planetary surface. The small holes (vesicles) are created by gas bubbles escaping as the magma cools and solidifies.

Uses & applications

Aggregates for construction, road base, concrete, and as a raw material for 'rock wool' insulation. Larger vesicular pieces are often used in landscaping or as 'lava rocks' for grills.

Geological facts

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

Field identification & locations

Identify in the field by its high density relative to other small stones, its dark color, and the presence of tiny pits or 'vesicles.' Commonly found in volcanic fields, oceanic islands (like Hawaii), and mid-ocean ridges.

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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

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Blue Apatite

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

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Magnetite

Magnetite (Fe3O4)

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