mineral
Botryoidal chalcedony (likely jasper/chalcedony aggregate)
Microcrystalline quartz, SiO₂; commonly iron-oxide stained
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; brown, cream, mustard-yellow, and reddish colors with a dull to waxy luster. Botryoidal mammillary surfaces and conchoidal fracture are typical; individual crystals are microscopic and cleavage is absent.
Identified More mineral →
Explore Botryoidal chalcedony (likely jasper/chalcedony aggregate) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness about 6.5–7 Mohs; brown, cream, mustard-yellow, and reddish colors with a dull to waxy luster. Botryoidal mammillary surfaces and conchoidal fracture are typical; individual crystals are microscopic and cleavage is absent.
Formation & geological history
Forms when silica-rich groundwater precipitates in cavities, replacing host rock or coating surfaces; iron oxides create the red-brown and yellow coloration. Its precise geological age cannot be determined from the photograph and depends on the deposit.
Uses & applications
Used as a lapidary stone for cabochons, carvings, polished specimens, and ornamental objects; attractive examples are collectible rather than major industrial material.
Geological facts
The rounded “grape-like” texture is called botryoidal or mammillary growth. The specimen may be marketed as botryoidal jasper, chalcedony, or iron-stained quartz, although exact naming requires testing and locality information.
Field identification & locations
Look for very fine texture, waxy luster, high hardness, and inability to scratch with a steel knife; a white streak and conchoidal fracture support chalcedony. Common occurrences include volcanic cavities and silica-rich replacement zones worldwide.
