igneous

Scoria (Lava Rock)

Vesicular Basalt / Scoria

Hardness: 5-6 Mohs; Color: Dark brown, black, or reddish-purplish; Luster: Dull/Earthly; Structure: Vesicular (pitted with gas bubbles); Cleavage: None; Specific Gravity: Low (often floats briefly/very lightweight due to air pockets).

Hardness: 5-6 Mohs
Color: Dark brown, black, or reddish-purplish
Luster: Dull/Earthly

Identified March 18, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the rapid cooling of basaltic or andesitic lava containing high gas content. As the lava erupts and pressure drops, gas bubbles expand and are trapped as the rock solidifies. Common in Cenozoic volcanic fields.

Uses & applications

Used extensively in landscaping, gas grill lava rocks, high-temperature insulation, lightweight concrete aggregate, and road drainage systems.

Geological facts

Scoria is different from pumice in that it has larger vesicles and thicker cell walls, making it dense enough to sink in water eventually, whereas pumice often floats indefinitely.

Field identification & locations

Identify by its 'Swiss cheese' appearance and lightweight feel. Commonly found near cinder cones and volcanic vents in regions like Iceland, Hawaii, and the Western United States. Collectors should look for unique glass-like inclusions.

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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