Likely amphibolite

Dark greenish-gray, coarse-grained and speckled with a slight sheen. Typical hardness is about 5–6 Mohs; minerals are interlocking, with no consistent cleavage visible at this scale.

Forms when basaltic or gabbroic rock is metamorphosed under medium- to high-grade heat and pressure. Amphibolites occur in metamorphic terranes spanning a wide range of geological ages.

Used locally as crushed stone, aggregate, and decorative building stone; attractive specimens may be collected.

Its characteristic dark amphibole minerals give amphibolite its name and commonly produce a hornblende-rich, foliated texture.

The specimen’s dark, sparkly, granular appearance is consistent with amphibolite, but a photograph cannot confirm the mineral assemblage. Look for hornblende’s elongated dark crystals alongside lighter feldspar; it is found in many mountain belts and ancient metamorphic shields.