mineral

Polished dark agate or jasper specimen

Cryptocrystalline quartz (chalcedony), SiO₂; exact identification is uncertain from the image

AI-generated identification · may be incorrect

Dark brown-to-black, irregularly patterned, waxy to subvitreous luster; hardness about 6.5–7 Mohs, no obvious cleavage, microcrystalline quartz structure, and specific gravity near 2.6. The surface appears polished or tumbled.

Identified August 22, 2026More mineral →

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At a glance

Common name: Polished dark agate or jasper specimen
Scientific name: Cryptocrystalline quartz (chalcedony), SiO₂; exact identification is uncertain from the image
Category: mineral
Identified: August 22, 2026
Method: Standard

AI Estimated Value

Approximately $5–$30 for a small common polished piece; $30–$150+ if unusually patterned, large, or from a recognized 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 formed when silica-rich fluids filled cavities in volcanic rock, later developing chalcedony and possibly iron/manganese staining; commonly Cenozoic to older, depending on locality.

Uses & applications

Used for cabochons, beads, carvings, ornamental objects, and lapidary specimens; not generally important as a construction stone in this form.

Geological facts

Agate and jasper can grade into one another: banded, translucent material is typically called agate, while opaque dark material is often marketed as jasper.

Field identification & locations

Identify by its quartz-like hardness, nonmetallic waxy polish, lack of cleavage, and inability to scratch with a steel blade; field certainty requires a close, unblurred view and ideally translucency or streak testing. Common worldwide, especially in volcanic terrains.