Glow up!
Fluorite, Meaning, Properties, and Facts
CaF2Mohs 4Isometric
Fluorite is calcium fluoride, a glassy mineral that grows in cubes and comes in almost every color. Below: what it is, its properties, where it is found, how to spot a fake, care, value and the meaning people give it.
What is fluorite
Fluorite is a halide mineral made of calcium and fluorine, and it is the reference mineral for 4 on the Mohs hardness scale. Most fluorite mined each year goes to industry under the trade name fluorspar, as a flux in steelmaking and as the raw material for hydrofluoric acid. The name comes from the Latin fluere, to flow, because it helps ore melt. The element fluorine is named after it, and so is fluorescence: in 1852 the physicist George Stokes coined that word for the glow some fluorite gives off under ultraviolet light.
Fluorite properties
Fluorite properties come down to four things: it is soft, glassy, heavier than quartz and quick to split. That last one is cleavage. Fluorite breaks cleanly in four directions, and many of the tidy octahedrons sold in shops were cleaved from larger pieces. Full mineral data is on Mindat's fluorite page.
| Mineral | Fluorite (a halide) |
|---|---|
| Chemistry | CaF2 (calcium fluoride) |
| Color cause | Trace elements and radiation damage; pure fluorite is colorless |
| Hardness | 4 on the Mohs scale |
| Crystal system | Isometric (cubic) |
| Luster | Glassy (vitreous) |
| Specific gravity | 3.18 |
| Main localities | China, Mexico, England, Spain, Illinois |
| Water safe | Quick rinse only |
| Sun safe | No: some colors fade in strong light |
Fluorite hardness
Fluorite hardness is 4 on the Mohs scale, softer than glass, a steel knife or quartz. Household dust carries tiny quartz grains, so wiping a dusty fluorite with a dry cloth can leave fine scratches, and a bowl of mixed tumbled stones will scuff it fast. With four cleavage directions it also chips easily, so store it on its own.
Where fluorite is found
Fluorite is found where hot, mineral-rich water moved through rock: in veins with lead and zinc ores, in cavities in limestone and in granite pegmatites. China mines the most, followed by Mexico. Collectors prize the green fluorite of Weardale in northern England, the purple and yellow cubes of Asturias in Spain and the old mines of southern Illinois, where fluorite is the state mineral. In Colorado it grows in the Pikes Peak pegmatites with smoky quartz and amazonite.
Fluorite crystal shapes and colors
Fluorite crystal shapes are mostly cubes, with natural octahedrons less common. A fluorite stone in a shop might also be cleaved, tumbled or cut into a tower. Colors run through purple, green, blue, yellow, pink and colorless, often in zones. Rainbow fluorite is banded purple, green and clear, each band recording a change in the fluid as the crystal grew. Yttrium fluorite is fluorite with some of its calcium replaced by the rare earth element yttrium. Many fluorites glow blue or violet under a UV flashlight, often from traces of europium. More on that glow in geology.com's guide to fluorescent minerals.
How to tell if fluorite is real
To tell if fluorite is real, look inside it and think about hardness. Real fluorite often shows flat cleavage cracks that flash rainbow colors and straight color bands that follow the crystal faces. Glass fakes show round bubbles, swirls and even color. Fluorite is too soft to scratch glass, so a piece that scratches a glass bottle is something else. Purple fluorite also gets sold as amethyst, which is quartz at Mohs 7 with no cleavage, and shelved beside lepidolite, which glitters with tiny mica flakes.
Fluorite care: water and sun
Fluorite care starts with water: it is water safe for a quick rinse in lukewarm water, then a soft cloth. Skip long soaks, salt, hot water, steam and ultrasonic cleaners, because sudden temperature changes and vibration can crack it along its cleavage. Sun is the other risk: some fluorite fades after long exposure to strong light, so keep it away from bright windows. More in water safe crystals and crystals that fade in the sun.
Fluorite price and value
Fluorite price and value depend on color, clarity, crystal shape, size and the mine it came from. Tumbled stones and polished points sit at the low end because fluorite is mined in bulk. Prices climb for sharp, undamaged crystals with strong or unusual color, good fluorescence and a famous locality on the label. Faceted fluorite exists, but it is a collector's stone, too soft for everyday jewelry.
Fluorite meaning and benefits
Fluorite meaning in crystal lore is focus and order, and the benefits people claim for it are a clearer head for study and work. That is belief, not chemistry; the same lore calls it the genius stone. The history is better documented. Some historians think the prized murrhine cups of ancient Rome were carved from fluorite, and Blue John, a purple and yellow banded fluorite from Castleton in Derbyshire, England, has been turned into bowls and vases since the 1700s.
Fluorite for sale
Fluorite for sale at geoslut arrives in drops. Every piece is one of one, photographed in daylight and labeled with its mineral and locality, and the list hears about each drop first.
Fluorite FAQ
Can fluorite go in water?
Fluorite can go in water for a quick rinse, but do not let it soak, and keep it out of salt water and hot water.
Does fluorite fade in the sun?
Fluorite can fade in the sun after long exposure, so display it out of direct light.
Why does fluorite glow under UV light?
Fluorite glows under UV light when trace elements such as europium absorb the ultraviolet and give it back as visible light, usually blue or violet.
Is fluorite rare?
Fluorite is not rare: millions of tons are mined every year for industry. Clean, colorful crystals from famous mines are much scarcer.