Fluorite is one of those crystals that seems almost determined to come in every colour it can possibly manage. Purple, green, blue, yellow, pink, clear, white, brown and even almost black specimens can all occur, and some crystals contain several colours in bands or zones within the same piece. It can be completely transparent, cloudy, or beautifully clear, and it often forms those wonderfully geometric cubic crystals that make Fluorite so recognisable.

Chemically, Fluorite is Calcium Fluoride (CaF₂) and has a Mohs hardness of just 4. That makes it considerably softer than Quartz, so while those perfect little cubes might look tough, Fluorite needs a bit more care than some of the harder crystals sitting beside it on a shelf. It also has perfect cleavage, meaning it can split quite easily along specific planes within its crystal structure.

The colours of Fluorite are caused by different impurities, defects and radiation effects within the crystal. This is why two Fluorite specimens from completely different places can look nothing alike. Some localities become famous for a particular colour or style, while others produce crystals showing several colours together. Colour zoning is especially common, producing those beautiful bands where one shade gradually changes into another.

This is where Rainbow Fluorite comes in. Despite the name, it isn't a separate mineral or a special species of Fluorite. Rainbow Fluorite is simply Fluorite that displays several colours, usually in distinct bands or zones within the same crystal. Greens, purples, blues, yellows and clear areas can appear together, sometimes with quite sharp boundaries between the colours and sometimes blending gradually into one another.

The colours form as the crystal grows, with changes in the chemical conditions around it affecting what happens within each stage of growth. Different impurities and defects can influence the colour, so a single crystal can essentially record several different moments in its formation. This is part of what makes Rainbow Fluorite so fascinating to look at. You're not necessarily looking at different pieces joined together. You're looking at one crystal whose appearance changed as it grew.

Rainbow Fluorite is particularly popular in crystal collecting and jewellery, although its relatively low hardness means it is better suited to pieces that won't be knocked about too much. Large polished towers, spheres and freeform pieces are common, as are naturally formed cubes showing bands of colour.

Fluorite has another little trick: it can glow.

Under ultraviolet light, some Fluorite specimens fluoresce in brilliant colours, often blue or blue violet, although green, red, pink, white and other colours can occur depending on the particular material and the elements involved. The word fluorescence actually comes from Fluorite itself. The effect was named after the mineral because it was one of the substances known to show this strange behaviour under ultraviolet light. Some Fluorite can also continue glowing for a short time after the UV source is removed, a phenomenon called phosphorescence.

Green, Yellow and Purple Fluorite under normal light

The same Fluorite specimens under UV light

The name Fluorite has an interesting connection to something that has nothing to do with crystals on a spiritual altar. It comes from the Latin fluere, meaning “to flow”, referring to Fluorite's use as a flux. When added to certain mineral mixtures during smelting, Fluorite helps them melt more easily. The mineral was officially named Fluorite in 1797, but its usefulness had already been recognised long before mineralogists gave it the name we use today.

That industrial side of Fluorite is easy to overlook when you're admiring a gorgeous purple cube, but it is actually one of the reasons Fluorite is important far beyond the world of gemstones. Fluorite, also known commercially as fluorspar, is an important source of fluorine and is used as a flux in metal production and in the manufacture of various fluorine compounds. It is also the starting material for producing hydrogen fluoride and hydrofluoric acid, which are used throughout the chemical industry.

Fluorite has also been appreciated for its beauty for a very long time.

The Romans were particularly fond of beautifully coloured fluorspar, carving it into vessels and other decorative objects. One Roman cup in the British Museum, made from fluorspar and found in a Roman-period tomb in ancient Cilicia, gives us a glimpse of just how valuable these objects could be. Ancient writers even recorded enormous prices being paid for some fluorspar cups, although the exact historical details surrounding those accounts are best treated with a little caution.

British Museum Roman Cup

One of the most famous varieties of Fluorite is Blue John, a particularly beautiful, banded Fluorite found in Derbyshire, England. Blue John is usually purple, blue, yellow or creamy-white, often with the colours arranged in distinctive bands and patterns. It became highly prized for ornamental stone and was carved into bowls, vases, candlesticks and other decorative objects.

The Derbyshire deposits are particularly interesting because Blue John became strongly associated with the region itself. By the nineteenth century, it was being used for elaborate decorative pieces, and examples can still be found in museums and historic collections. The British Museum describes Blue John as the finest-quality fluorspar and notes that its supply had become severely depleted by the end of the nineteenth century.

Blue John Fluorite

Fluorite also has a habit of growing in some wonderfully precise shapes. Cubes are probably the form most people associate with it, but octahedral crystals can occur too, along with combinations of different crystal faces. Some specimens develop multiple generations of Fluorite, with newer crystals growing over older ones. Others contain ghostly internal bands, colour zones or inclusions that record different stages of the crystal's growth.

There are famous Fluorite localities all over the world, each producing material with its own personality. England is particularly well known for colourful Fluorite from places such as Derbyshire and the northern Pennines. China produces enormous quantities of collector-quality material in a huge range of colours and forms, while Mexico, the United States, Germany, Spain and many other countries have produced their own spectacular specimens.

One of the things collectors love about Fluorite is that locality can make such a difference. A green Fluorite from one mine may look completely different from a green Fluorite from another. Some deposits produce incredibly clear cubes, others produce deep purple crystals, and some are known for unusual colour zoning or combinations with minerals such as Quartz and Calcite.

Cubed Purple Fluorite

In modern crystal and spiritual practices, Fluorite is commonly associated with clarity, focus, organisation, protection and mental energy. Purple Fluorite is often connected with intuition and spiritual awareness, while green Fluorite is sometimes associated with growth, balance and the Heart Chakra. Practitioners may use Fluorite during meditation, study, planning, energy work or rituals where they want to bring a sense of order to a particularly busy mind.

It is also often described as a crystal for clearing away mental clutter. That association isn't an ancient belief that can be traced neatly back to one particular culture. It belongs largely to modern crystal traditions, where Fluorite's orderly crystal structure and striking geometric forms have helped shape its symbolism.

And honestly, Fluorite does have a rather appropriate appearance for a crystal associated with organisation. Those neat little cubes look as though someone actually sat down and made a plan.

Cubed Blue Fluorite

Then you turn one over and find purple, green and blue all growing into one another, so perhaps the lesson is not necessarily perfect order. Maybe it's more about finding some sort of pattern in the beautiful chaos.

Either way, Fluorite manages to be a gemstone, an industrial mineral, a scientific curiosity, a historical carving material and a favourite modern crystal all at once.

And if you happen to put it under UV light and discover that your apparently ordinary Fluorite suddenly starts glowing, well... that's just Fluorite reminding you that it had another trick hiding up its sleeve.