mineral
Amethyst Geode
Silicon Dioxide (SiO2) with iron impurities
Hardness: 7 (Mohs scale); Color: Purple/Violet; Luster: Vitreous/Glassy; Crystal Structure: Trigonal/Hexagonal prisms; Cleavage: None/Conchoidal fracture; Specific Gravity: 2.65
- Hardness
- 7 (Mohs scale)
- Color
- Purple/Violet
- Luster
- Vitreous/Glassy
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Physical properties
Hardness: 7 (Mohs scale); Color: Purple/Violet; Luster: Vitreous/Glassy; Crystal Structure: Trigonal/Hexagonal prisms; Cleavage: None/Conchoidal fracture; Specific Gravity: 2.65
Formation & geological history
Formed in volcanic rocks (basalt) when gas cavities are filled with silica-rich fluids and iron, then irradiated by surrounding rock over many thousands of years.
Uses & applications
Used widely in jewelry, as decorative display specimens, and in spiritual/metaphysical practices.
Geological facts
The purple color comes from trace amounts of iron and aluminum combined with natural radiation. If heated to high temperatures, amethyst will turn yellow and is often sold as 'heat-treated citrine'.
Field identification & locations
Identify by hexagonal crystal terminations and purple color. Commonly found in Brazil, Uruguay, and Africa. Look for rounded volcanic nodules with a dull exterior containing crystals inside.
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