igneous

Basalt with Calcite Veins

Basalt (Mafic Volcanic Rock)

Hardness: 5-6 (Mohs); Color: Dark grey to charcoal with white veins; Luster: Dull/Matte (basalt) to Vitreous (calcite); Crystal Structure: Fine-grained aphanitic matrix; Cleavage: None in basalt, rhombohedral in veins.

Hardness: 5-6 (Mohs)
Color: Dark grey to charcoal with white veins
Luster: Dull/Matte (basalt) to Vitreous (calcite)

Identified May 9, 2026More igneous →

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Physical properties

Formation & geological history

Formed from rapid cooling of magnesium-rich and iron-rich lava. The white veins are typically calcite or quartz that precipitated from hydrothermal fluids filling fractures long after the rock solidified.

Uses & applications

Commonly used in construction as crushed stone, road base, or decorative garden stones. High-quality smooth river stones are used in massage therapy and landscaping.

Geological facts

Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. The white veins act as a geological 'history book,' showing where the rock cracked under tectonic stress.

Field identification & locations

Identify by its heavy weight (high density), dark color, and fine texture. The white veins will often react (fizz) with weak acid if they are calcite. Commonly found on beaches and in volcanic regions.

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

Blue Apatite

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

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Magnetite

Magnetite (Fe3O4)

mineral