igneous

Lava Rock (Basalt)

Basalt (extrusive igneous rock)

Hardness: 6 (Mohs); Color: Dark gray to black; Luster: Dull to earthy; Crystal structure: Aphanitic (fine-grained) to porphyritic, often with vesicular (bubbly/porous) texture; Cleavage: None; Specific Gravity: 2.7-3.3

Hardness: 6 (Mohs)
Color: Dark gray to black
Luster: Dull to earthy

Identified November 7, 2025More igneous →

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Physical properties

Formation & geological history

Formed from rapidly cooling basaltic lava flows at the Earth's surface. The numerous small holes (vesicles) are formed by gas bubbles escaping as the lava cools and solidifies. Geological age varies widely, from recent volcanic eruptions to billions of years old.

Uses & applications

Construction (crushed stone, aggregate, decorative landscaping), gardening (mulch, planting medium), essential oil diffusers (due to porous nature), jewelry (beads, pendants), insulation material, and historically for tools and building materials.

Geological facts

Basalt is the most common rock type on Earth's crust, forming the bulk of oceanic crust. It is also found on the Moon, Mars, and other terrestrial planets. The dark color is due to its high content of iron and magnesium-rich minerals.

Field identification & locations

Field identification: Black to dark gray color, fine-grained, and most notably, the vesicular texture (small holes) which gives it a sponge-like appearance and light weight compared to other dense rocks. Often found near volcanoes, mid-ocean ridges, and areas of ancient volcanic activity. Common locations include Hawaii, Iceland, the Pacific Northwest of the USA, and much of the ocean floor. For collectors, the vesicular texture and dark color are key identifiers.

Other igneous specimens

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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

Blue Apatite

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

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Magnetite

Magnetite (Fe3O4)

mineral