sedimentary

Likely graywacke or fine-grained metamorphic rock

Quartz–feldspar–mica-rich lithic sandstone (tentative; image alone is insufficient for exact identification)

AI-generated identification · may be incorrect

Dark gray, fine-grained, dull to slightly silky surface with a prominent pale vein or fracture fill. Likely Mohs hardness 5–7, massive texture, and no obvious crystal cleavage; the pale line may be quartz or calcite.

Identified September 16, 2026More sedimentary →

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At a glance

Common name: Likely graywacke or fine-grained metamorphic rock
Scientific name: Quartz–feldspar–mica-rich lithic sandstone (tentative; image alone is insufficient for exact identification)
Category: sedimentary
Identified: September 16, 2026
Method: Standard

AI Estimated Value

Typically $1–$10 as an unlabelled specimen; $10–$30 if locality-documented or unusually attractive.

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

If graywacke, it formed from rapidly deposited submarine turbidity flows, commonly during Paleozoic–Mesozoic sedimentation; later fracturing allowed vein minerals to form. Exact age and process require locality and testing.

Uses & applications

Commonly used as crushed stone, aggregate, riprap, and occasionally decorative stone; this small specimen has mainly educational or modest collecting value.

Geological facts

The sharp contrast between dark host rock and light vein is typical of healed fractures. A vinegar test on the vein can suggest calcite if it effervesces, while quartz will not.

Field identification & locations

Look for poorly sorted grains and sedimentary layering for graywacke; a glassy vein that scratches glass suggests quartz. Common in accretionary mountain belts and ancient submarine-fan deposits.