igneous

Olivine Basalt

Mafic Volcanic Rock (rich in (Mg, Fe)2SiO4)

Hardness: 6-7 on Mohs scale. Color: Dark gray to black matrix with olive-green phenocrysts. Luster: Dull (matrix) to vitreous (crystals). Structure: Aphanitic with porphyritic texture. Specific gravity: 2.8-3.0.

Hardness: 6-7 on Mohs scale
Color: Dark gray to black matrix with olive-green phenocrysts
Luster: Dull (matrix) to vitreous (crystals)

Identified March 19, 2026More igneous →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the Earth's surface. These specimens are typically associated with oceanic crust and volcanic hotspots.

Uses & applications

Used in construction as crushed stone or aggregate. High-quality olivine crystals (peridot) are used in jewelry. Also used as a flux in steel making.

Geological facts

Olivine is one of the first minerals to crystallize from a cooling magma. Some olivine-rich rocks (peridotites) originate from the Earth's mantle and are brought to the surface by volcanic eruptions.

Field identification & locations

Identify by looking for green, glassy 'grains' embedded in a dark, heavy rock. Found in volcanic regions like Hawaii, Iceland, and the Canary Islands. It is magnetic if high in iron content.

Other igneous specimens

See all

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