sedimentary

Polymictic conglomerate (possibly impact breccia)

Lithified polymictic conglomerate/breccia; clasts appear mainly mafic volcanic rock, with quartz- or feldspar-rich fragments in a dark matrix

AI-generated identification · may be incorrect

Coarse, poorly sorted angular-to-subrounded clasts in a black, fine-grained matrix; likely hardness about 5–6 overall, dull to slightly vitreous luster, no consistent cleavage, and specific gravity roughly 2.7–3.1. The contrasting pale clasts and dark matrix are diagnostic.

Identified September 10, 2026More sedimentary →

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At a glance

Common name: Polymictic conglomerate (possibly impact breccia)
Scientific name: Lithified polymictic conglomerate/breccia; clasts appear mainly mafic volcanic rock, with quartz- or feldspar-rich fragments in a dark matrix
Category: sedimentary
Identified: September 10, 2026
Method: Standard

AI Estimated Value

About $5–$30 for a common hand specimen; $50–$200+ if provenance confirms a notable impact structure or unusual composition.

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

Formed when varied rock fragments accumulated and became cemented, or when shattered material was welded/lithified after impact or violent volcanism. Exact age and origin cannot be established from the photograph alone.

Uses & applications

Primarily a geological/educational or collector specimen; comparable durable conglomerates and breccias can be used as decorative stone or aggregate, but this small piece has no major industrial value.

Geological facts

Conglomerate contains rounded clasts, whereas breccia contains predominantly angular clasts; this specimen appears transitional and may be impact-related if unusually shocked or enriched in melt-like matrix.

Field identification & locations

Look for clast boundaries, contrasting lithologies, and a cemented matrix; a hand lens, acid test, and thin section would help distinguish breccia from conglomerate. Similar rocks occur in volcanic terrains, fault zones, and impact structures worldwide.