mineral

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Clear to white (milky); Luster: Vitreous (glassy); Crystal Structure: Hexagonal/Trigonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Clear to white (milky)
Luster: Vitreous (glassy)

Identified March 4, 2026More mineral →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 7 on Mohs scale; Color: Clear to white (milky); Luster: Vitreous (glassy); Crystal Structure: Hexagonal/Trigonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed in cavities within volcanic or sedimentary rocks where hydrothermal fluids or groundwater deposit silica layers over millions of years, often during the Cenozoic or Mesozoic eras.

Uses & applications

Used in gemstone collecting, home decor, and educational displays. Industrial quartz is used in electronics (oscillators) and glassmaking.

Geological facts

Geodes are often called 'thunder eggs' in certain regions. The word geode comes from the Greek word 'geoides' meaning earth-like.

Field identification & locations

Identify by the hollow center lined with inward-pointing crystals and a rough, drab outer 'rind'. Found commonly in desert regions like Morocco, Brazil, and the Midwestern United States (Keokuk area).