mineral

Geode fragment, likely quartz-lined basalt or chalcedony nodule

Microcrystalline quartz (SiO₂), possibly with iron-oxide staining in a basaltic host

AI-generated identification · may be incorrect

Dark brown-gray, irregular broken specimen with a small cavity and pale blue-gray crystalline/drusy interior; quartz hardness 7, vitreous luster, no cleavage, and specific gravity about 2.65. The outer material may be weathered basalt or iron-stained chalcedony, but the image is not sufficient for certainty.

Identified August 13, 2026More mineral →

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At a glance

Common name: Geode fragment, likely quartz-lined basalt or chalcedony nodule
Scientific name: Microcrystalline quartz (SiO₂), possibly with iron-oxide staining in a basaltic host
Category: mineral
Identified: August 13, 2026
Method: Standard

AI Estimated Value

Approximately $2–$15 for a small ordinary fragment; $20–$75 if the cavity has well-formed, attractive crystals.

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

Gas bubbles or cavities in volcanic lava later became lined or filled by silica-rich groundwater, commonly during the Cenozoic or older volcanic episodes. Iron oxides produced the brown coloration through weathering.

Uses & applications

Used as a decorative or collecting specimen; attractive drusy quartz is sometimes set in jewelry, while similar geode material is used for display and lapidary work.

Geological facts

A fresh broken surface may show sparkling quartz crystals, whereas chalcedony appears waxy and smooth. Acid does not react with quartz, and quartz can scratch ordinary glass.

Field identification & locations

Common in volcanic regions and basalt fields, including the western United States, Mexico, Brazil, and Uruguay. Confirm with a glass-scratch test, close inspection for quartz sparkle, and testing the dark host separately.