igneous
Basalt chip
Aphanitic mafic extrusive rock
AI-generated identification · may be incorrectHardness 6 on Mohs scale; dark gray to black color; dull to sub-vitreous luster; fine-grained, microcrystalline to cryptocrystalline structure with no visible crystals.
Identified More igneous →
Explore Basalt chip in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness 6 on Mohs scale; dark gray to black color; dull to sub-vitreous luster; fine-grained, microcrystalline to cryptocrystalline structure with no visible crystals.
Formation & geological history
Formed from the rapid cooling of low-viscosity, iron- and magnesium-rich lava flows at the Earth's surface.
Uses & applications
Commonly used in construction aggregate, road base, railroad ballast, and sometimes in stonework and landscaping.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the ocean basins and also forms much of the volcanic islands worldwide.
Field identification & locations
Identify in the field by its dark, heavy, fine-grained appearance, often found in volcanic regions, riverbeds, and glacial drift.
