igneous

Olivine-bearing Basalt / Scoria

Mafic Igneous Rock (primarily (Mg, Fe)2SiO4)

Hardness: 6-7 (Mohs); Color: Dark grey to black groundmass with prominent olive-green phenocrysts; Luster: Vitreous to dull; Crystal structure: Orthorhombic (olivine crystals); Cleavage: Poor; Specific Gravity: 2.7–3.3.

Hardness: 6-7 (Mohs)
Luster: Vitreous to dull

Identified February 25, 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 through the rapid cooling of magnesium-rich and iron-rich lava at or near the Earth's surface. The green olivine crystals often crystallize early in the cooling magma chamber before being erupted. This type of rock is common in volcanic hotspot regions like Hawaii and Iceland.

Uses & applications

Used primarily in construction as road base or aggregate. High-quality olivine crystals (Peridot) are used in jewelry. In industrial settings, it is used as a flux in steelmaking and as a casting sand.

Geological facts

Olivine is one of the first minerals to crystallize from magma and is the most common mineral in the Earth's upper mantle. Specimens found on the moon by Apollo astronauts were often high in olivine content.

Field identification & locations

Identify in the field by checking for a dark, often vesicular (holed) or fine-grained matrix containing translucent green 'glassy' grains. Commonly found in basaltic lava flows and volcanic fields. Collectors should look for large, clear green crystals known as 'bombs' or 'xenoliths'.

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