igneous
Epidote-bearing basalt
Basalt with epidote-group mineral inclusions, likely epidote or pistachite (Ca₂(Al,Fe³⁺)₃(SiO₄)₃(OH))
AI-generated identification · may be incorrectFine-grained, dark gray to black, with olive-green rounded crystals or patches and a dull to slightly glassy luster. Basalt has hardness about 5–6 Mohs; epidote is 6–7, with no obvious cleavage visible in this tumbled specimen.
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Physical properties
Fine-grained, dark gray to black, with olive-green rounded crystals or patches and a dull to slightly glassy luster. Basalt has hardness about 5–6 Mohs; epidote is 6–7, with no obvious cleavage visible in this tumbled specimen.
Formation & geological history
Basalt forms from rapidly cooled mafic lava, commonly in oceanic crust and volcanic fields; epidote develops later through hydrothermal alteration of calcium- and iron-rich basalt. The specimen’s exact geological age and locality cannot be determined from the image.
Uses & applications
Primarily a collector specimen or lapidary curiosity; rarely used decoratively when polished. Basalt is widely used as crushed aggregate and building stone, but this small piece has no practical industrial value.
Geological facts
The contrasting pistachio-green color is characteristic of epidote-group minerals, although visual identification alone cannot distinguish epidote from chlorite, prehnite, or other green alteration minerals.
Field identification & locations
Look for a dense, fine-grained black basalt matrix containing hard olive-green grains or veins; a streak, hardness, and specific-gravity test—or laboratory analysis—would confirm the minerals. Commonly found in altered volcanic rocks and oceanic terrains.
