mineral

Tumbled black-and-white stone, likely dendritic agate or jasper

Cryptocrystalline quartz (SiO₂), possibly chalcedony with manganese-oxide dendrites

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque cream-white with black branching or irregular inclusions and a dull-to-waxy polish. It has no visible cleavage and a fine microcrystalline quartz structure; exact identification is limited by the photograph.

Identified August 11, 2026More mineral →

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At a glance

Common name: Tumbled black-and-white stone, likely dendritic agate or jasper
Scientific name: Cryptocrystalline quartz (SiO₂), possibly chalcedony with manganese-oxide dendrites
Category: mineral
Identified: August 11, 2026
Method: Standard

AI Estimated Value

$2–$15 for a common tumbled piece; approximately $20–$75 if unusually patterned, large, or verified as natural dendritic agate.

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

Silica-rich groundwater filled cavities or fractures in volcanic rock, while manganese or iron oxides produced the dark patterns; formation commonly occurred during the Cenozoic or older volcanic episodes. Tumbled surfaces are human-processed.

Uses & applications

Used primarily as a decorative stone, lapidary material, cabochon, and inexpensive collectible; it has little industrial value in this form.

Geological facts

Dendritic patterns are mineral inclusions, not fossils or plant material. Similar black-and-white tumbled stones may also be Picasso jasper, zebra jasper, or dyed chalcedony.

Field identification & locations

Commonly found as tumbled material from Brazil, Madagascar, India, Mexico, and the western United States. A glassy scratch-resistant surface, waxy luster, and lack of cleavage support chalcedony; a streak, translucency test, and magnification would refine identification.