differentiating purple Amethyst and purple Fluorite.

Sometimes rough purple fluorite and quartz Amethyst look a lot a like.  I have pieces that visually, it is very hard tell the difference. In fact, sometimes identifying the mineral and its core is quite challenging and near impossible for some individuals in the market looking to purchase the stones.  Especially if the Fluorite or Quartz Amethyst is not showing the natural cleavage or have not been cut and/or polished into shapes.  For example, both can be the same color with the same variance in lightness/darkness of color. But the two minerals are very different. Fluorite's chemical formula is CaF2, meaning the mineral is composed of Fluorine and Calcium in equal amounts. Quartz's chemical formula is SiO2.

If cut and polished into shapes though, differences may become even harder to tell visually.

Quartz and fluorite also naturally glows under ultraviolet (UV) light. UV light will only show they are real crystals, not specify which type they are.  So, if you’re questioning the authenticity of your crystal, stick it under a blacklight. The electrons in the crystals will naturally react to the UV light, giving off a fluorescent glow. If there’s no glow, the crystal is most likely fake.

Note:  different crystal of the same type will glow at different UV spectrums.  In fact, one crystal may glow one color at one UV spectrum and glow a different color at another.

How do you test Fluorite and Quartz?

In general, both can be tested by checking: 

• luster/shine
• how soluble with water
• hardness

What are the differences?

Is crystal shiny or dull? Raw, untreated Fluorite is dull, but can be polished to a shine. Quartz is a naturally shiny.  But Fluorite can be easily shined.

Does the crystal dissolve in water? Fluorite will dissolve very slowly in water, but it can be submerged for a small amount of time. At room temperatures quartz is practically insoluble in water and the dissolution process in water is extremely slow, so there is no need to worry about quartz crystals being damaged by repeated cleaning.

Does the crystal scratch easily? Fluorite is a soft crystal, so it scratches easily. Quartz is much harder than Fluorite. The surface of real fluorite has a lot of tiny scratches due to its low hardness. It has a hardness rating of 4 on the Mohs hardness scale - Fluorite easily fractures. Amethyst rates a 7 on the Mohs scale and has good toughness.  Amethyst should be able to scratch metals and glass.