Stone of the Week - Fluorite

Fluorite, also known as Fluorspar, is made up of calcium fluoride (CaF2). The name fluorite is derived from the Latin fluo, meaning "flow", because it is slightly dissolvable in water. Fluorite belongs to the Isometric crystal system, otherwise known as the cubic crystal system. This means that its most basic form (properly called a ‘unit cell’) is a cubic shape; hence the crystals are commonly cubic.

Fluorite can be found in a vareity of beautiful colors including blue, pink, blue-green, and purple.

Fluorite can occur as a variety of colors, including green, blue, purple, pink, yellow, and white. These colors can occur as angular banding, commonly referred to as ‘chevron’ banding. A neat property of fluorite is that it is fluorescent – in fact this is where the term fluorescent came from. When held under UV light, the electrons inside the fluorite become ‘excited’ resulting in their energy level increasing – when they come back down from this ‘excited state’ light is released. Usually in fluorite this will be blue, but other colors are known to occur.

Fluorite can often be found as cubic crystals (left) and a bit more rarely this gorgeous chevron banding (right).

In the United States, the state of Illinois is the most abundant location for fluorite, and is the official mineral of Illinois. This area is often called the ‘fluorspar district’, and was mined until 1995 when the last mine closed – now it’s a popular location for rockhounds to collect specimens. Another famous locale for fluorite is in Castleton in Derbyshire, England. Here there is a unique blue and purple fluorite called ‘Blue John’ and is used for ornamental stone. Fluorite is a popular stone for jewelry work, though care must be taken as it is a ‘soft’ stone with a hardness of 4 on the Mohs hardness scale.

Fluorite makes for a beautiful stone to use in jewelry and ornamental work.

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Fluorite Facts:
Chemical composition: CaF2
Crystal System: Isometric
Color: blue, green, purple, pink, white/clear, yellow, brown, red, black
Habit: Crystals, Granular, Massive
Fracture: Uneven, Conchoidal
Cleavage: Perfect
Luster: Vitreous
Transparency: Transparent
Hardness: 4
Specific Gravity: 3.3
Streak: White
Occurrence: Worldwide, but most commonly in the US and UK
Other: Fluorescence, some specimens may exhibit thermoluminescence

References

Rocks, Minerals, & Fossils of the World by C. Pellant and R. Phillips. Published 1990 by Little, Brown and Co. ISBN: 0316697966

Wikipedia – Fluorite. http://en.wikipedia.org/wiki/Fluorite