metamorphic

Quartz-rich metamorphic rock, likely quartzite

Quartzite; predominantly crystalline SiO₂ with minor feldspar, mica, and iron-oxide minerals

AI-generated identification · may be incorrect

Typically gray to white, granular, and vitreous to sugary-lustrous, with interlocking quartz crystals; quartz hardness is Mohs 7, no cleavage, and specific gravity about 2.6. The dark patches likely represent biotite, graphite, amphibole, or iron-stained inclusions.

Identified September 16, 2026More metamorphic →

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Physical properties

Formation & geological history

Forms when quartz-rich sandstone is recrystallized under heat and pressure during regional metamorphism, commonly during mountain building. Its exact geological age cannot be determined from the photograph and depends on the host formation.

Uses & applications

Used as durable building stone, aggregate, slabs, and landscaping material; attractive pieces may be collected or polished, though this specimen appears mainly of educational interest.

Geological facts

Quartzite commonly breaks across grains rather than around them, producing a hard, splintery fracture. It is often confused with quartz-rich granite, but quartzite lacks clearly visible large feldspar crystals and igneous texture.

Field identification & locations

Identify it by testing whether a steel file fails to scratch it and whether fresh fractures cut through quartz grains; acid produces no reaction. Common occurrences include metamorphic mountain belts worldwide, including the Appalachians, Alps, Himalaya, and western United States.