sedimentary

Chalcedony in Matrix (likely Agatized Coral or Chert)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale), Color: tan, grey, white, translucent blue-grey, Luster: waxy to dull, Crystal Structure: Trigonal (microcrystalline), Specific gravity: 2.6-2.64

Hardness: 6

Identified July 18, 2026More sedimentary →

Explore Chalcedony in Matrix (likely Agatized Coral or Chert) in the encyclopedia →

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Physical properties

Hardness: 6.5-7 (Mohs scale), Color: tan, grey, white, translucent blue-grey, Luster: waxy to dull, Crystal Structure: Trigonal (microcrystalline), Specific gravity: 2.6-2.64

Formation & geological history

Formed through the replacement of calcium carbonate or organic material with silica-rich groundwater. Common in sedimentary environments and fossilized reefs, often dating from the Eocene to Miocene epochs.

Uses & applications

Used for lapidary work, jewelry (when polished), aquarium decor, and as collective mineral specimens.

Geological facts

This specimen appears to be a form of silicated sedimentary rock where rhythmic cavities (vugs) are filled or lined with chalcedony. It shares many characteristics with Florida Agatized Coral, which was named the state stone of Florida in 1979.

Field identification & locations

Identify by its hardness (cannot be scratched by a steel knife) and its botryoidal or waxy translucent interiors within a rough, pitted limestone-like exterior. Commonly found in coastal or riverbed sediments in the Southeast USA.