metamorphic

Hornblende-bearing metamorphic rock (likely amphibolite)

Amphibolite, chiefly hornblende amphibole and plagioclase feldspar

AI-generated identification · may be incorrect

Dark gray to black, coarse-grained, granular texture with scattered pale feldspar and rusty weathering. Amphibole hardness is about 5–6 Mohs, vitreous to dull luster, no obvious cleavage at specimen scale, and typical specific gravity is approximately 2.9–3.2.

Identified September 5, 2026More metamorphic →

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Physical properties

Formation & geological history

Forms when basaltic or gabbroic protoliths undergo medium- to high-grade regional metamorphism, commonly during mountain building. Its age depends on locality and may range from Precambrian to younger Paleozoic or Mesozoic terranes.

Uses & applications

Used locally as crushed stone, aggregate, riprap, and occasionally dimension stone; attractive polished pieces may be collected but it is not generally a gemstone.

Geological facts

The specimen’s dark amphibole-rich appearance and pale granular minerals are consistent with amphibolite, though a photograph cannot exclude hornblende gneiss, mafic schist, or altered basalt.

Field identification & locations

Identify it by its heavy, dark color, interlocking crystals, and abundant black amphibole with pale feldspar; amphibolite occurs in metamorphic belts worldwide, including the Appalachians, Canadian Shield, and Scandinavian Shield.