sedimentary
Quartz Geode
Silicon dioxide (SiO2)
Hardness of 7 on the Mohs scale, brownish-grey outer chalcedony layer with sparkling clear or white quartz crystals lining the interior cavity, vitreous luster inside, conchoidal fracture on the outer shell, trigonal crystal system.
Identified More sedimentary →
Explore Quartz Geode in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness of 7 on the Mohs scale, brownish-grey outer chalcedony layer with sparkling clear or white quartz crystals lining the interior cavity, vitreous luster inside, conchoidal fracture on the outer shell, trigonal crystal system.
Formation & geological history
Formed in hollow cavities in sedimentary and volcanic rocks where silica-rich groundwater percolated through over millions of years, slowly depositing quartz crystals inward from the cavity walls.
Uses & applications
Used widely in lapidary arts, decorative items, jewelry making, and as popular specimens for mineral and rock collections.
Geological facts
Geodes appear as ordinary, unassuming lumps of rock on the outside, but cracking or cutting them open reveals a stunning, hidden world of glittering crystals.
Field identification & locations
Look for rounded, nodular stones with a bumpy or weathered exterior texture in areas with limestone, dolomite, or volcanic ash deposits. Tapping them gently with a geological hammer often reveals a hollow sound indicating a geode.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sedimentary Sandstone
Arenite (Sedimentary Rock)
sedimentary
Fossiliferous Concretion
Septarian Concretion containing Brachiopods/Crinoids
fossil
Banded Siltstone / Mudstone Pebble
Siltstone / Argillite
sedimentary
Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
sedimentary
Shale
Shale (clastic sedimentary rock)
sedimentary