igneous
Basalt (Beach Pebble)
Basalt (Aphanitic Mafic Igneous Rock)
Hardness: 6.0; Color: Dark grey to black; Luster: Dull/Matte (tumbled); Crystal Structure: Fine-grained/Aphanitic; Specific Gravity: 2.8-3.0
- Hardness
- 6
- Color
- Dark grey to black
- Luster
- Dull/Matte (tumbled)
Identified More igneous →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.0; Color: Dark grey to black; Luster: Dull/Matte (tumbled); Crystal Structure: Fine-grained/Aphanitic; Specific Gravity: 2.8-3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at the earth's surface. This specific specimen has been rounded by fluvial or marine erosion.
Uses & applications
Commonly used as decorative garden stones, in construction as aggregate, for hot stone massage therapy, and as aquarium substrate.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. It is also found extensively on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight for its size, and absence of visible large crystals. Often found on volcanic coastlines or in riverbeds draining volcanic regions.
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