Identity

Formula Ca5(PO4)3F
Class Phosphates
Crystal System Hexagonal
Hardness 5
Color Green, blue, purple, yellow, brown, colorless
Lustre Vitreous to resinous
Specific Gravity 3.2
Cleavage Indistinct
Streak White
Technical notes (click to open)(click to close)
Identity The fluorine member of the apatite group, and the most common apatite
Group Forms a series with chlorapatite and hydroxylapatite as the anion changes
Economic role Sedimentary phosphate rock is the world's main source of phosphorus for fertilizer
Teeth Tooth enamel is hydroxylapatite; fluoride shifts its surface toward acid resistant fluorapatite
Habit Hexagonal prisms; green, blue, purple, yellow, or brown

Name & Human History

Etymology

Fluorapatite is the most common member of the apatite family, a group of phosphate minerals. The apatite name comes from a Greek word meaning to deceive. It was given because apatite is so often mistaken for other minerals. It comes in many colors and shapes. Fluorapatite is the form that holds fluorine, and it is by far the most widespread. It usually grows as green, blue, or brown six sided crystals.

Today

Fluorapatite is hugely important, though it rarely makes the news. Vast beds of it, mined as phosphate rock, are the main source of phosphorus for the world's fertilizers. Without it, modern farming could not feed the planet. Clear, well colored crystals are also cut as collector gems. They are soft, though, and best kept for display rather than daily wear.

Geology & Occurrence

Formation

Fluorapatite forms in many settings. It crystallizes from cooling magma in igneous rocks. It grows in veins from hot fluids. And it builds up in great sedimentary beds on ancient sea floors. Those sea floor beds, made of countless tiny phosphate grains, are the ones mined for fertilizer. Fine crystals come instead from veins and pockets in harder rock.

Notable Localities

Fine fluorapatite crystals come from many places. Deep green ones come from the Pyrenees, purple ones from Maine and Germany, and fine blue ones from Brazil. Mexico produces clear yellow gems, and Portugal and Canada yield large crystals. The huge phosphate beds mined for fertilizer lie in Morocco, Florida, and Russia.

Did you know?

Fluorapatite is closer to you than any specimen on a shelf. The hard enamel of your teeth is built from a cousin mineral, hydroxylapatite. When fluoride from toothpaste or water meets your enamel, it slowly turns the surface toward fluorapatite, which resists acid better. That tiny change is why fluoride helps fight cavities. The same mineral that feeds the world's crops also helps guard your smile.

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