Fluorite

Fluorite is frequently fluorescent, i.e. it will glow under ultra-violet light. This occurs because certain electrons in the mineral absorb the energy from the ultra-violet light and jump to a higher energy state. The fluorescent light is emitted when those electrons jump down to a lower energy state and emit a light of their own.

Rare examples of fluorite may exhibit phosphorescence, i.e. they will continue to glow when removed from the ultra-violet light source. This occurs because electrons in the mineral have stored energy from the ultra-violet light which they then emit on a delayed basis.

Rare examples of fluorite may exhibit thermoluminescence, i.e. they will glow when heated. This occurs because the mineral may contain chemical bonds that emit light when thermal energy (heat) is applied.

An even rarer property sometimes exhibited by fluorite is triboluminescence, where minerals glow when they are crushed, struck, scratched or even rubbed in some cases. The minerals contain chemical bonds that emit light when mechanical energy is applied to them.

Fluorite is a common vein mineral associated with mineral deposits.

fluorite (dark purple).

Chemical composition - CaF ₂
Hardness - 4
Specific gravity - 3.2
Transparency - Transparent to translucent
Colour - White if pure, but extremely variable - purple, blue, green, yellow, colourless, reddish orange, pink, white, brown; a single crystal can be multi-coloured
Streak - White
Lustre - Vitreous
Cleavage/fracture - Perfect in 4 directions forming octahedrons / hackly
Crystal habit/mode of occurrence - Prismatic, always equant (typically cubes and to a lesser extent octahedrons as well as combinations of the two) / less common are crusts and botryoidal forms