mineral

Quartz Geode Fragment

Silicon Dioxide (SiO2)

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

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

Identified March 30, 2026More mineral →

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Physical properties

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

Formation & geological history

Formed as secondary deposits from hydrothermal fluids or groundwater rich in silica. These fluids fill cavities (vugs) in igneous or sedimentary rock. This specimen likely formed over thousands of years as crystals grew inward from the cavity walls. Often found in Mississippian or Jurassic age strata.

Uses & applications

Commonly used as decorative specimens, in educational kits, for gemstone collecting, and historically in glass making or early watch mechanics (due to piezoelectric properties).

Geological facts

Geodes are known as 'earth eggs.' While the outer shell looks like a common rock, the interior can contain a variety of minerals. Quartz is the most common mineral found inside geodes because of its resistance to weathering.

Field identification & locations

Identify in the field by looking for rounded, hollow nodules that feel lighter than they look. If cracked, they reveal a crystalline interior. Commonly found in desert regions of the SW United States, Brazil, and Uruguay. Collectors should look for undamaged crystal terminations.