mineral
Quartz Geode (Amethyst / Clear Quartz)
Silicon Dioxide (SiO2)
Hardness: 7 on Mohs scale. Color: Pale translucent purple to clear/greyish with reddish-brown iron oxide inclusions. Luster: Vitreous (glassy). Crystal Structure: Hexagonal/Trigonal. Cleavage: None (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Luster
- Vitreous (glassy)
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Physical properties
Hardness: 7 on Mohs scale. Color: Pale translucent purple to clear/greyish with reddish-brown iron oxide inclusions. Luster: Vitreous (glassy). Crystal Structure: Hexagonal/Trigonal. Cleavage: None (conchoidal fracture).
Formation & geological history
Formed in cavities within volcanic rocks (basalt/rhyolite) or sedimentary rocks where silica-rich groundwater precipitation allowed internal crystal growth over millions of years.
Uses & applications
Popular for mineral collections, home decor, metaphysical practices, and lapidary cutting or display.
Geological facts
Geodes are hollow, sub-spherical rock formations containing internal crystal cavities. The word 'geode' comes from the Greek word 'Geoides' meaning 'earth-like'.
Field identification & locations
Identified by a round or egg-shaped hollow structure lined with inward-pointing quartz crystals. Commonly found in Brazil, Uruguay, Morocco, and parts of the Midwestern USA (Iowa, Indiana).
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