metamorphic

Rounded quartz-rich cobble, possibly quartzite

Quartzite (mostly microcrystalline quartz, SiO₂); identification tentative from the photograph

AI-generated identification · may be incorrect

Pale tan-gray, rounded and weathered, with a dull to weakly vitreous luster and faint granular texture. Quartzite is typically Mohs 7, has no cleavage, conchoidal to irregular fracture, and specific gravity around 2.65; the rusty areas likely represent iron-oxide staining.

Identified September 19, 2026More metamorphic →

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At a glance

Common name: Rounded quartz-rich cobble, possibly quartzite
Scientific name: Quartzite (mostly microcrystalline quartz, SiO₂); identification tentative from the photograph
Category: metamorphic
Identified: September 19, 2026
Method: Standard

AI Estimated Value

About $0–$5 as an ordinary cobble; roughly $10–$30 if unusually attractive, polished, or demonstrably from a notable locality.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Formation & geological history

Likely a glacial or river-rounded clast derived from metamorphosed sandstone; quartzite commonly forms during regional metamorphism, generally in Precambrian to Paleozoic terrains. Around 46.4°N, 23.9°E (Transylvania), transported quartz-rich metamorphic or sedimentary clasts are geologically plausible.

Uses & applications

Usually a low-value field specimen; quartzite is used as aggregate, road stone, building stone, and occasionally decorative material. Attractive pieces may be polished, but this specimen shows limited gem value.

Geological facts

Quartzite forms when sandstone recrystallizes so thoroughly that quartz grains interlock, making it harder and more resistant than the original sandstone.

Field identification & locations

Test with a steel knife: it should resist scratching; quartz will scratch glass, though the rounded surface may be difficult to test. A vinegar test is not diagnostic; a streak test and close inspection for visible quartz grains can help distinguish it from limestone or ordinary sandstone.