igneous
Basalt
Basalt (Aphanitic Mafic Rock)
Hardness: 6 (Mohs); Color: dark grey to black; Luster: dull to sub-metallic; Crystal structure: fine-grained (aphanitic), typically contains pyroxene and plagioclase feldspar; Specific Gravity: 2.8–3.0
- Hardness
- 6 (Mohs)
- Color
- dark grey to black
- Luster
- dull to sub-metallic
Identified More igneous →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6 (Mohs); Color: dark grey to black; Luster: dull to sub-metallic; Crystal structure: fine-grained (aphanitic), typically contains pyroxene and plagioclase feldspar; 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 the surface of a terrestrial planet or a moon. It is the most common volcanic rock on Earth, making up most of the ocean floor and large continental provinces.
Uses & applications
Used extensively in construction as an aggregate, road base, railroad ballast, and in the production of high-strength stone wool insulation. Also used in decor and as dimension stone.
Geological facts
Basalt is the primary rock type of the lunar maria on the Moon and covers vast areas of Mars and Venus. Giant's Causeway in Northern Ireland is a famous example of columnar basalt joints.
Field identification & locations
Identify by its dark color, heavy weight (relative to size), and fine-grained texture which lacks visible crystal grains to the naked eye. Commonly found in volcanic regions and oceanic crustal exposures.
More like this
Other igneous specimens
Granite
Granite
Igneous
Granite
Granite
Igneous
Blue Apatite
Fluorapatite (Ca5(PO4)3F)
mineral
Dalmatian Jasper
Aplite with Arfvedsonite inclusions
igneous
Magnetite
Iron(II,III) oxide (Fe3O4)
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