igneous

Basalt (Vesicular and Ropey)

Vesicular Basalt / Pahoehoe Basalt

Hardness: 5-6 (Mohs scale); Color: Dark grey, black, or reddish-brown due to oxidation; Luster: Dull/Earthy; Structure: Vesicular (pitted with gas bubbles) and ropey (Pahoehoe) texture; 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 May 3, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the rapid cooling of magnesium-rich and iron-rich lava (basaltic) erupted from a volcano. The holes (vesicles) are created by trapped gas bubbles. The ropey texture indicates a flow that had a low viscosity.

Uses & applications

Used in landscaping (lava rocks), as an ingredient in concrete, for road base, and as high-quality stone for grilling or sauna heat retention.

Geological facts

Basalt is the most common rock in Earth's crust and makes up most of the ocean floor. The ropey texture shown in parts of this specimen is called Pahoehoe, a Hawaiian term meaning 'smooth, unbroken lava'.

Field identification & locations

Identify by its dark color, heavy weight (relative to size, unless extremely vesicular), and the presence of small holes or flow patterns. Commonly found in volcanic fields like those in Hawaii, Iceland, or the Pacific Northwest.

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

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)

mineral

Magnetite

Magnetite (Fe3O4)

mineral