metamorphic

Weathered quartz-rich metamorphic rock (probable gneiss or quartzite)

Biotite–quartz–feldspar gneiss, possibly micaceous quartzite

AI-generated identification · may be incorrect

Hardness about 6–7 Mohs; cream, gray, tan, and black mottling with a dull to vitreous luster. Visible quartz/feldspar grains and dark mica or iron-oxide staining; weak foliation appears present, though the small weathered specimen limits certainty.

Identified September 16, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when quartz- and feldspar-rich sedimentary or igneous rock underwent high-temperature regional metamorphism, likely during Precambrian or younger mountain-building events. Weathering produced the brown staining and rounded surface.

Uses & applications

Used as dimension stone, aggregate, landscaping material, and occasionally as a lapidary or teaching specimen; this piece has little commercial gemstone value.

Geological facts

The dark patches may be biotite, amphibole, or manganese/iron oxides, so a precise identification requires a fresh surface, streak, hardness, and ideally thin-section or chemical testing.

Field identification & locations

Look for interlocking quartz and feldspar, mica-rich dark bands, and foliation; quartz will scratch glass, while feldspar generally will not scratch quartz. Common in ancient metamorphic terrains worldwide.