Igneous

Scoria

Vesicular Basalt / Scoria (Mafic silicate rock)

Hardness: 5-6 Mohs. Color: Typically reddish-brown to dark grey/black. Luster: Dull or earthy. Structure: Highly vesicular (honeycombed with gas bubbles). Cleavage: None. Specific gravity: Low (often floats briefly, though denser than pumice).

Hardness: 5-6 Mohs
Color: Typically reddish-brown to dark grey/black
Luster: Dull or earthy

Identified February 18, 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 basaltic or andesitic lava under high pressure. Gas bubbles are trapped as the lava solidifies near the surface of volcanic vents or on the surface of lava flows during Cenozoic to recent eruptions.

Uses & applications

Used extensively in landscaping and decorative gardens, as lightweight aggregate in drainage systems, for high-temperature insulation in gas grills (lava rocks), and in road construction for traction.

Geological facts

Unlike its cousin pumice, scoria is mafic and usually sinks in water due to its thicker cell walls and higher iron content. It is a primary component of cinder cones, which are formed by explosive fountaining of lava.

Field identification & locations

Identify by its 'Swiss cheese' appearance, rough/abrasive texture, and reddish-brown oxidation. Commonly found in volcanic regions like Iceland, Hawaii, the Canary Islands, and the Western United States. Collectors should look for unique aerodynamic shapes known as spindle bombs.

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