igneous
Vesicular Basalt (Iron Scoria)
Aphanitic Mafic Igneous Rock with Vesicular Texture
Hardness: 5-6 Mohs. Color: Dark grey to charcoal black with reddish-brown oxidation. Luster: Dull/Earthy. Structure: Fine-grained (aphanitic) matrix with spherical cavities (vesicles). Specific gravity: 2.8–3.0.
- Hardness
- 5-6 Mohs
- Color
- Dark grey to charcoal black with reddish-brown oxidation
- Luster
- Dull/Earthy
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Physical properties
Hardness: 5-6 Mohs. Color: Dark grey to charcoal black with reddish-brown oxidation. Luster: Dull/Earthy. Structure: Fine-grained (aphanitic) matrix with spherical cavities (vesicles). Specific gravity: 2.8–3.0.
Formation & geological history
Formed from the rapid cooling of magnesium and iron-rich (mafic) lava. The holes (vesicles) are created by gas bubbles trapped as the lava solidified. The specimen location in Albury-Wodonga sits near the edge of the Newer Volcanics Province of SE Australia.
Uses & applications
Commonly used in landscaping, as a road base material, for heat retention in BBQ grills, and as an abrasive in stone-washing textiles. High iron content makes it a popular specimen for educational geology kits.
Geological facts
While it looks like a meteorite due to the dark color and 'craters', the presence of round gas vesicles is a definitive indicator of terrestrial volcanic origin rather than space rock origin.
Field identification & locations
Identify by the many small pits or holes and its relatively high density compared to pumice. It will not float in water. It is extremely common in the volcanic plains of Victoria and Southern NSW.
