igneous
Orbicular gabbro (likely orbicular norite)
Gabbroic rock containing plagioclase, pyroxene, and orbicules; white veins may be calcite or felsic alteration
AI-generated identification · may be incorrectDark, coarse-grained mafic matrix with pale concentric orbicules and irregular white mineral-filled fractures. Typical hardness is about 6–7; luster is dull to subvitreous, with interlocking crystalline texture and no consistent cleavage at the rock scale.
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Physical properties
Dark, coarse-grained mafic matrix with pale concentric orbicules and irregular white mineral-filled fractures. Typical hardness is about 6–7; luster is dull to subvitreous, with interlocking crystalline texture and no consistent cleavage at the rock scale.
Formation & geological history
Slow cooling of mafic magma produced the gabbroic texture; orbicules formed through episodic crystal growth and chemical changes in the magma. White veins formed later during hydrothermal alteration, generally in Precambrian to younger intrusive complexes.
Uses & applications
Primarily a collector and decorative stone; attractive polished slabs may be used for countertops, tiles, or ornamental objects, though it is uncommon commercially.
Geological facts
Orbicular varieties are rare and prized for their circular structures, which may consist of plagioclase-rich shells around darker cores. The image could also represent a related orbicular diorite or altered gabbro, which requires thin-section or chemical analysis for certainty.
Field identification & locations
Identify it by its dark crystalline matrix, pale rounded orbicules, and contrasting vein networks; a fresh surface and streak, hardness, and acid tests help distinguish carbonate veins. Notable occurrences include Finland, Corsica, Madagascar, and parts of Scandinavia.
