Fluorite Fluorite (also called fluorspar) is a mineral composed of calcium fluoride, CaF2. It is an isometric mineral with a cubic habit, though octahedral and more complex isometric forms are not uncommon. Cubic crystals up to 20Crystal twinning is common and adds complexity to the observed crystal habits.The word fluorite is derived from the Latin root fluo, meaning "to flow" because the mineral has a relatively low melting point and was used as an important flux in smelting.