igneous

Lava Rock (Scoria)

Extrusive basaltic scoria

Hardness: 5-6 (Mohs scale); Color: Dark reddish-brown to black; Luster: Dull/Earthy; Structure: Highly vesicular (pitted with gas bubbles); Cleavage: None; Specific Gravity: Low (often floats in water temporarily until saturated).

Hardness: 5-6 (Mohs scale)
Color: Dark reddish-brown to black
Luster: Dull/Earthy

Identified March 25, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the rapid cooling of gas-rich basaltic lava erupted from a volcano. The holes (vesicles) are created by gas bubbles that were trapped as the magma solidified. Usually found in Cenozoic volcanic fields.

Uses & applications

Commonly used in landscaping as decorative ground cover, in high-temperature gas grills (lava rocks), as lightweight aggregate in concrete, and for drainage in horticulture.

Geological facts

Scoria is similar to pumice but has larger vesicles and thicker cell walls, making it denser and darker. Because it is formed from basaltic magma, it contains more iron and magnesium than light-colored pumice.

Field identification & locations

Identify in the field by its sponge-like appearance, lightweight feel, and rough, abrasive texture. Commonly found near cinder cones and volcanic vents in places like Arizona, Iceland, and Italy.

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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