mineral
Amethyst cluster
Amethyst, purple quartz (SiO₂)
AI-generated identification · may be incorrectTypically purple, vitreous luster, hexagonal quartz crystals, no cleavage, conchoidal fracture, Mohs hardness 7, and specific gravity about 2.65. The specimen appears to be a natural crystal cluster, possibly on a pale quartz or host-rock base.
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Physical properties
Typically purple, vitreous luster, hexagonal quartz crystals, no cleavage, conchoidal fracture, Mohs hardness 7, and specific gravity about 2.65. The specimen appears to be a natural crystal cluster, possibly on a pale quartz or host-rock base.
Formation & geological history
Forms when iron-bearing silica-rich groundwater fills cavities in volcanic rocks; irradiation and heat produce the purple color. Most deposits formed in Mesozoic–Cenozoic volcanic environments, especially in Brazil, Uruguay, Zambia, and Mexico.
Uses & applications
Used as a lapidary and jewelry stone, ornamental specimen, and decorative geode material; it has no major industrial use beyond quartz-related applications.
Geological facts
Amethyst is the purple variety of quartz, with color ranging from lilac to deep violet; heating can turn it yellow or orange, producing citrine-like material.
Field identification & locations
Identify it by purple transparent-to-translucent quartz crystals, glassy luster, hardness 7, and lack of cleavage; it will scratch glass but not be scratched by a steel knife. Common sources include basalt cavities in Brazil and Uruguay.
