igneous
Basalt
Basalt (primarily Plagioclase feldspar and Pyroxene)
Hardness: 6 (Mohs), Color: Dark grey to black, Luster: Dull to sub-metallic (fine-grained), Crystal Structure: Aphanitic (fine-grained), Specific Gravity: 2.8 - 3.0
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 (fine-grained), Crystal Structure: Aphanitic (fine-grained), Specific Gravity: 2.8 - 3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the Earth's surface. Found in oceanic crust, volcanic islands, and continental flood basalts.
Uses & applications
Used extensively in construction as road base, concrete aggregate, railroad ballast, and for floor tiles or monuments.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floors. It is also found on the Moon and Mars.
Field identification & locations
Identify in the field by its dark color, fine-grained texture, and high density. Commonly found in former volcanic regions or areas with tectonic activity.
More like this
Other igneous specimens
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
Sodalite
Sodalite - Na8(Al6Si6O24)Cl2
mineral
Blue Apatite
Apatite (Group), Ca5(PO4)3(F,Cl,OH)
mineral
Magnetite
Magnetite (Fe3O4)
mineral