igneous
Polished black stone, likely basalt
Basalt; mainly plagioclase feldspar, pyroxene, and minor olivine/iron oxides
AI-generated identification · may be incorrectFine-grained, opaque black to dark gray, with subdued vitreous-to-waxy luster; Mohs hardness about 5–6, massive texture, and no visible cleavage. The elongated form is human-shaped and polished, so diagnostic features are partly obscured.
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Physical properties
Fine-grained, opaque black to dark gray, with subdued vitreous-to-waxy luster; Mohs hardness about 5–6, massive texture, and no visible cleavage. The elongated form is human-shaped and polished, so diagnostic features are partly obscured.
Formation & geological history
Basalt forms when low-viscosity mafic lava cools rapidly at or near Earth’s surface, commonly in volcanic fields and oceanic crust. Most examples range from Precambrian to modern, but this specimen’s age cannot be determined visually.
Uses & applications
Used as crushed aggregate, roadstone, paving, dimension stone, and occasionally as a polished decorative or grounding stone. This shaped piece has primarily ornamental or collecting value.
Geological facts
Basalt is the most abundant volcanic rock on Earth and commonly forms broad lava plateaus and oceanic seafloor. It may contain tiny vesicles or faint crystals that become more apparent under magnification.
Field identification & locations
Identify it by its black, dense, fine-grained appearance, lack of fizz in dilute acid, and absence of glassy conchoidal fracture; a magnet may respond weakly due to iron minerals. Common localities include Hawaii, Iceland, India’s Deccan Traps, and oceanic volcanic regions.
