Fluorite from Cave-in-Rock, Illinois USA

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This beautiful translucent specimen of Fluorite comes from Cave-in-Rock, Illinois, USA and shows a deep purple under good light.

Fluorite is an important industrial mineral composed of calcium and fluorine (CaF2) and is also known as Fluorspar. It is very easy to identify as it is the only common mineral that has four directions of perfect cleavage, often breaking into pieces with the shape of an octahedron. Crystal twinning is common and adds complexity to the observed crystal habits.

Fluorite normally glows a blue-violet colour under short-wave UV (ultraviolet) and long-wave UV light. Some specimens can glow a cream or white colour while many specimens do not fluoresce at all. Another interesting point is that the term “fluorescence” came from George Gabriel Stokes in 1852 after illuminating a specimen with light.

I acquired this specimen from Greg at Blue Gems Minerals at the August 2016 Sydney Crystal Show.

Specimen Details

Chemical Formula: CaF2

ID #: JG0012

Colour: This specimen is a nice deep purple when viewed in good light.
Fluorite comes in various other colours, including colourless, green, white, blue, pink, red, yellow, orange, brown, gray and black. It can also be multicoloured and banded.

Hardness: 4

Acquisition Date: 06/08/2016

Crystal System: Isometric

Lustre: Vitreous

Dimensions: 76mm x 68mm x 82mm

Weight: 392g

Location: Cave-in-Rock, Illinois, USA

Rarity of Mineral

Very Common

Did you know!?
The term fluorescence was derived from the mineral name Fluorite. Generally it fluoresces blue but other fluorescent colours include red, green, yellow, white and purple. Some will even demonstrate phosphorescence.

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