Amethyst vs Fluorite
Amethyst and Fluorite are easy to confuse. Here’s how they stack up on the properties that actually separate them.
| Amethyst | Fluorite | |
|---|---|---|
| Also known as | Quartz (Quartz family) | — |
| Colour | Purple | Purple, Green, Blue, Clear, Red, Yellow |
| Mohs hardness | 7 (lower in impure varieties) | 4 (defining mineral) |
| Lustre | Vitreous/glassy | Vitreous |
| Streak | White | White |
| Crystal system | Trigonal | Isometric |
| Transparency | Transparent to translucent | Transparent to translucent |
| Cleavage | None | Octahedral, perfect on {111}, parting on {011} |
| Fracture | Conchoidal | Subconchoidal to uneven |
| Chemical formula | Silica (silicon dioxide, SiO) | CaF 2 |
| Specific gravity | 2.65 constant; variable in impure varieties | 3.175–3.184; to 3.56 if high in rare-earth elements |
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Frequently asked questions
What's the easiest way to tell Amethyst from Fluorite?
Hardness is the quickest test: Amethyst is Mohs 7 (lower in impure varieties) and Fluorite is Mohs 4 (defining mineral).