Amethyst
Silicate (quartz variety) · SiO₂
Amethyst is the purple variety of quartz, coloured by trace iron and natural irradiation, and one of the most popular collectable gemstones.
What is amethyst?
Amethyst is quartz coloured purple by trace iron and natural radiation. It ranges from the faintest lilac to a deep royal purple and commonly lines the inside of volcanic geodes as sparkling crystal crusts. Heating amethyst turns it yellow, producing most commercial citrine. Despite its gem status it is common enough to be affordable and is a favourite first purple crystal for new collectors.
Properties
- Chemical formula
- SiO₂
- Category
- Silicate (quartz variety)
- Hardness (Mohs)
- 7
- Crystal system
- Trigonal
- Lustre
- Vitreous
- Streak
- White
- Colour
- Pale lilac to deep purple
- Cleavage / fracture
- None; conchoidal fracture
How to identify amethyst
- →Purple colour in glassy, six-sided quartz crystals.
- →Hardness 7, scratches glass, no cleavage, conchoidal fracture.
- →Colour often zoned, strongest near the crystal tips.
- →Frequently found as a crystal-lined cavity (geode or vug).
Where amethyst is found
Major sources are Brazil and Uruguay (giant geodes), Zambia, and historic sites in Mexico, Russia and Thunder Bay in Canada. Small amethyst occurrences are scattered worldwide.
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