mineral

Quartz Geode

Silicon Dioxide (SiO2)

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

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

Identified May 27, 2026More mineral →

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Physical properties

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

Formation & geological history

Formed as secondary mineral precipitates in hollow cavities (vesicles) within volcanic or sedimentary rocks. Silica-rich water seeps into the cavity and cools or evaporates, leaving behind crystalline growth. Geological age varies by source rock.

Uses & applications

Used primarily for educational specimens, home decor, metaphysical collections, and lapidary work. Pure quartz is also used in electronics and glass manufacturing.

Geological facts

Geodes are essentially 'rock bubbles.' While the exterior looks like an ordinary, drab stone, the interior is hollow and lined with crystals. Some of the world's largest quartz geodes are found in Brazil and Uruguay.

Field identification & locations

Identify in the field by looking for rounded, bumpy nodules that feel lighter than they look (indicating a hollow center). Often found in desert regions or areas with limestone/volcanic beds. Collectors use a rock hammer or tile saw to reveal the crystals inside.