igneous
Possible pyrite-bearing gabbro or diorite
Coarse-grained mafic/intermediate intrusive rock; likely plagioclase + amphibole/pyroxene with disseminated pyrite (FeS₂)
AI-generated identification · may be incorrectDark gray-green, granular, and weakly metallic with scattered brassy grains; likely Mohs 6–7 overall, with pyrite at 6–6.5, no obvious cleavage, and crystalline interlocking texture. The specimen appears unpolished and weathered.
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Physical properties
Dark gray-green, granular, and weakly metallic with scattered brassy grains; likely Mohs 6–7 overall, with pyrite at 6–6.5, no obvious cleavage, and crystalline interlocking texture. The specimen appears unpolished and weathered.
Formation & geological history
Likely crystallized slowly from magma deep in the crust, producing visible interlocking crystals; its exact age and locality cannot be determined from the image. Surface alteration may account for the greenish-gray appearance.
Uses & applications
Mostly a collecting specimen or teaching sample; gabbro/diorite are used as crushed stone, aggregate, and dimension stone, while pyrite has limited industrial sulfur and mineral-collection value.
Geological facts
Pyrite’s brassy metallic grains can resemble gold but are harder, more brittle, and commonly form cubic crystals. The photograph does not resolve the minerals well enough for a definitive species identification.
Field identification & locations
Look for a dense, coarse crystalline texture, dark plagioclase-rich matrix, and brassy grains that leave a greenish-black streak rather than a gold-yellow streak. Common related rocks occur in continental and oceanic intrusive complexes worldwide.
