I’m looking at a piece of fluorite on my desk. It measures about five inches by three, and it is basically a chunk of grey-coloured stone, quite heavy, its top surface slightly rough and bubbled in texture. It looks almost like a miniature cobbled street – except that the cobbles are all sparkling with tiny crystals.
And half-buried in the surface of this ‘street’ are cubes of fluorite, some just less than an inch across, others much smaller; semi-transparent like coloured glass, they contain distinct pigments of turquoise and purple which seem to swirl together without blending.
Fluorite is composed of calcium and fluorine, and it is one of the commonest minerals in the world. In its purple form it resembles amethyst, although it is softer than quartz and has different properties.
I was also amazed to find out how many colours fluorite can display: in addition to greenish blue and purple, its crystals can be white, black, colourless, red, pink, deep green or bright yellow. The colour is determined by the activities of the electrons in the mineral. (I am not about to explain the activities of electrons: I am still grappling with the idea that they can be in two places at once. Thank the ever-watchable Professor Cox for that!)
The word ‘fluorite’ comes from the Latin, fluere, which means ‘to flow’, and refers to the fact that it was used as a flux or flowing agent in the process of smelting metals. Amazingly, this was known as far back as Roman times: the Romans loved to do a bit of mining, and they soon recognised the benefits of fluorite, which occurs – very conveniently – within many ore-bearing rocks. Today, fluorite is still used in the steel-making industry, and in the production of ceramic glass, enamels and high-performance camera lenses.
What is even more interesting is the fact that fluorite glows in ultra-violet light; this is where the word ‘fluoresce’ comes from. Some specimens have also been found to glow in the dark for brief periods after being heated or exposed to strong sunlight. Just imagine stumbling into a cave of glowing fluorite – no wonder crystals have been prized since the dawn of time!
Fluorite is beautiful in any of its colour variations. I’ve seen some lovely specimens of deep green and brilliant yellow, although most of the examples in rock and fossil shops are of the purple-and-turquoise variety. Highly prized by collectors are the rare reds and pinks, which occur in the French and Swiss Alps.
In Britain, we have our own claim to fame: at Castleton in Derbyshire, a unique type of fluorite called ‘Blue John’ has been mined for at least 100 years, originally as a by-product of the lead mining industry. Blue John is characterised by its distinct stripes of deep purple alternating with cream or yellow, and it was so admired during the late 19th and early 20th centuries that it was used to carve a host of decorative urns and bowls. Many of these are on display at Chatsworth House in the Peak District.
In terms of crystal healing, fluorite is believed to alleviate the symptoms of arthritis, and to fend off cold and ‘flu viruses. It brings order to chaos, helps with concentration, and it is an effective protection against the low-level electromagnetic fields generated by computer screens. One site describes it as ‘the genius stone’. I think I’ll keep this piece on my desk!
Photos copyright © Colin & Jo Woolf unless otherwise stated
Please take a look at my other features on rocks and minerals: