mineral
Amethyst (Geode/Cluster)
Silicon Dioxide (SiO2) with iron impurities
Hardness: 7 (Mohs scale); Color: Pale lavender to deep violet; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: None; Specific Gravity: 2.65
- Hardness
- 7 (Mohs scale)
- Color
- Pale lavender to deep violet
- Luster
- Vitreous (glassy)
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Physical properties
Hardness: 7 (Mohs scale); Color: Pale lavender to deep violet; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: None; Specific Gravity: 2.65
Formation & geological history
Formed in hydrothermal veins or as geodes in volcanic rock. Magma/gas bubbles create cavities where silica-rich fluids crystallize over millions of years, primarily in the Cretaceous period specimens from South America.
Uses & applications
Widely used in jewelry (as a gemstone), home decor, metaphysical collecting, and as a birthstone (February).
Geological facts
The purple color comes from irradiation, iron impurities, and the presence of trace elements. It was once considered one of the 'Cardinal Gems' alongside diamond and ruby until large deposits were found in Brazil.
Field identification & locations
Identify by the macrocrystalline quartz structure and distinctive purple hue. Common in Brazil and Uruguay geodes. Look for hexagonal points and a white or grey outer rind (host rock).
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