igneous
Tumbled orbicular gabbro (likely oceanic gabbro)
Gabbro; chiefly plagioclase feldspar and pyroxene, with possible olivine, amphibole, and magnetite
AI-generated identification · may be incorrectCoarse-grained, dark green-black and gray rock with rounded pale feldspar-rich patches; granular crystalline texture and generally weak cleavage. Hardness is about 6–7 Mohs, with a dull to subtly glassy polished luster and high density (~2.9–3.2 g/cm³).
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Physical properties
Coarse-grained, dark green-black and gray rock with rounded pale feldspar-rich patches; granular crystalline texture and generally weak cleavage. Hardness is about 6–7 Mohs, with a dull to subtly glassy polished luster and high density (~2.9–3.2 g/cm³).
Formation & geological history
Forms when mafic magma cools slowly deep underground, commonly in oceanic crust; the orbicular pattern may reflect mineral segregation or alteration. Exact geological age cannot be determined from the photograph.
Uses & applications
Used as a decorative tumbled stone, lapidary material, countertop or architectural aggregate, and occasionally in cabochons; quality is mainly ornamental rather than gem-grade.
Geological facts
The pale rounded areas are likely feldspar-rich domains rather than true mineral “eyes.” Gabbro is the intrusive equivalent of basalt and commonly forms the lower parts of oceanic crust.
Field identification & locations
Identify it by its heavy weight, coarse interlocking black minerals, pale feldspar patches, and lack of vesicles or layering; a streak, hardness, and thin-section test would confirm it. Similar material occurs in ophiolites and mafic intrusive complexes worldwide.
