igneous
Basalt Breccia
Volcanic Breccia (composed of basaltic clasts in a fine-grained matrix)
Hardness: 5-6 (Mohs); Color: Grey, brown, and tan tones with dark inclusions; Luster: Dull/Earthy; Crystal Structure: Aphanitic to porphyritic fragments; Specific Gravity: 2.8-3.0
- Hardness
- 5-6 (Mohs)
- Color
- Grey, brown, and tan tones with dark inclusions
- Luster
- Dull/Earthy
Identified More igneous →
Explore Basalt Breccia in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-6 (Mohs); Color: Grey, brown, and tan tones with dark inclusions; Luster: Dull/Earthy; Crystal Structure: Aphanitic to porphyritic fragments; Specific Gravity: 2.8-3.0
Formation & geological history
Formed in volcanic environments through the breaking and re-cementing of igneous rock during eruptions or tectonic activity. These fragments are held together by a mineral cement or a fine-grained volcanic ash matrix.
Uses & applications
Primarily used as construction aggregate, road base material, and decorative landscaping stone.
Geological facts
Volcanic breccias can form through several processes including explosive eruptions, tectonic faulting of solidified lava, or even as part of a volcanic mudflow known as a lahar.
Field identification & locations
Identify by looking for angular, broken rock fragments (clasts) fused together in a solid matrix. Common in volcanic regions such as the Pacific Northwest, Iceland, and Hawaii.
