mineral
Polished quartz geode slice
Quartz (SiO₂), likely chalcedony-lined geode with drusy quartz crystals
AI-generated identification · may be incorrectHardness 7 (quartz); gray-white, translucent to opaque, with a dark hollow center and sparkling crystalline rim. Vitreous to waxy luster; quartz is trigonal and lacks cleavage, with conchoidal fracture. The dark area may be iron/manganese staining or inclusions, not necessarily amethyst.
Identified More mineral →
Explore Polished quartz geode slice in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness 7 (quartz); gray-white, translucent to opaque, with a dark hollow center and sparkling crystalline rim. Vitreous to waxy luster; quartz is trigonal and lacks cleavage, with conchoidal fracture. The dark area may be iron/manganese staining or inclusions, not necessarily amethyst.
Formation & geological history
Forms when silica-rich groundwater fills gas vesicles or cavities in volcanic rock, depositing chalcedony and later quartz crystals. The specimen’s exact geological age and locality cannot be determined from the image; geodes commonly form in Cenozoic to Paleozoic volcanic or sedimentary settings.
Uses & applications
Used as a decorative display stone, cabochon, paperweight, or jewelry component; not generally used structurally.
Geological facts
The exterior was cut and polished, revealing an internal cavity lined with microcrystalline quartz. A strong glassy sparkle and lack of obvious banding distinguish it from many agates.
Field identification & locations
Identify by its rounded nodule shape, quartz hardness, crystalline cavity, and conchoidal fracture; common sources include Brazil, Uruguay, Mexico, Morocco, and the United States. Exact identification would benefit from locality, hardness, and acid/magnet tests.
