igneous
Polished labradorite-rich gabbro (probable)
Gabbro, composed mainly of plagioclase feldspar and pyroxene, with possible labradorite
AI-generated identification · may be incorrectDark gray-black, coarse crystalline texture, subdued metallic/glassy luster, and irregular fractures; Mohs hardness about 6–7, with no obvious cleavage visible. The blue-gray flashes may be labradorescence from feldspar, though the image is insufficient for certainty.
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Physical properties
Dark gray-black, coarse crystalline texture, subdued metallic/glassy luster, and irregular fractures; Mohs hardness about 6–7, with no obvious cleavage visible. The blue-gray flashes may be labradorescence from feldspar, though the image is insufficient for certainty.
Formation & geological history
A mafic intrusive igneous rock crystallized slowly from magma deep within Earth, commonly during Precambrian to Phanerozoic crustal formation; polishing has rounded and enhanced its surface.
Uses & applications
Used as dimension stone, countertops, tiles, monuments, and decorative or lapidary specimens. Attractive labradorescent pieces are sold as cabochons or polished stones.
Geological facts
Gabbro is the coarse-grained underground equivalent of basalt. Labradorite-bearing varieties can show spectral blue, green, or gold flashes when rotated in light.
Field identification & locations
In the field, identify its heavy, dark, crystalline appearance and interlocking pale feldspar grains; a streak, hardness test, and thin-section or chemical analysis would distinguish it from basalt, diabase, or metallic ore. Common in oceanic crust and large mafic intrusions, including Norway, Canada, Madagascar, and the United States.
