mineral
Amethyst Geode
Amethyst (Silicon Dioxide with Iron impurities, SiO2)
Hardness: 7 on Mohs scale; Color: Pale violet to deep purple; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: None; Specific Gravity: 2.65.
- Hardness
- 7 on Mohs scale
- Color
- Pale violet to deep purple
- Luster
- Vitreous (glassy)
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Physical properties
Hardness: 7 on Mohs scale; Color: Pale violet to deep purple; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: None; Specific Gravity: 2.65.
Formation & geological history
Formed in volcanic rocks (basalts) where gas bubbles created cavities. Hydrothermal fluids rich in silica and trace amounts of iron deposited crystals over millions of years, typically during the Cretaceous period.
Uses & applications
Used extensively in jewelry, as decorative display pieces (geodes), for metaphysical purposes, and as a birthstone for February.
Geological facts
Amethyst was considered a precious stone on par with diamonds until large deposits were found in Brazil. The name comes from the Greek 'amethystos', meaning 'not intoxicated', due to a belief it prevented drunkenness.
Field identification & locations
Identify by its purple hue and hexagonal crystal points inside a rocky (often basaltic) rind. Found commonly in Brazil, Uruguay, and Madagascar. Collectors look for deep 'grape' purple color and clarity.
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