Apatite

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Kathy Feick

Apatite was named in 1788 for the Greek word apatite, which means “to deceive”, since apatite has a similar appearance to many other minerals. Apatite is not actually a specific mineral, but rather, is a name for a group of similar isomorphous hexagonal phosphate minerals. It can be very difficult to distinguish between the individual members since they partially replace each other, so a distinction is rarely made and they are instead all called apatite. 

Interesting fact: The bones and teeth of most animals, including humans, are composed of calcium phosphate, which is the same material as apatite.

Colouration:

Apatite can be colourless, white, yellow, brown, gray, red, pink, purple, blue, or green. Some specimens are even multicoloured. Colouration is often due to the presence of rare earth elements or natural irradiation.

pink apatite specimen mounted on wood

Apatite. Renfrew Co. Ontario. University of Waterloo Earth Sciences Museum Collection.

Varieties:

Apatite is identified by the chemical formula Ca5(PO4). It forms in hexagonal crystals and is a rock phosphate mineral. Apatite can exist in many different forms, along with other minerals, as long as the base of apatite calcium (Ca5) and phosphorous (PO4) exist together. There are three common forms of apatite that appear in nature. The three apatites are distinguished by the ions in their crystal lattice. It is important to note that all three varieties are usually present in every specimen although some specimens may have close to 100% of one ion or another. There are many more, but these are the most common three.

Fluroapatite (Ca5(PO4)3F): Fluroapatite is a major component in the enamel in teeth. It has fluorine in its chemical structure which makes this variety fluorescent. It is harder than hydroxylapatite though it is not as resistant to acids

Hydroxyl Apatite (Ca5(PO4)3OH): Hydroxyl apatite is the variety of apatite which has an OH group in its structure. Hydroxyl apatite is a major component in the enamel in teeth. It also composes 70% of bone material in the human body. It is more resistant to acids than fluroapatite though it is not as hard.

Chloroapatite (Ca5(PO4)3Cl): Cholroapatite is the variety of apatite with chlorine in its structure. It is commonly coloured white, yellow or light pink.

green apatite crystal

Apatite Crystal, Unknown Locality. University of Waterloo Earth Sciences Museum Collection.

Uses:

  • Manufacture of fertilizer
  • Occasional use as a gemstone
  • Index mineral on Mohs scale of hardness (hardness of 5)
  • As an ore of phosphate (it is the most common phosphate mineral) to be used in:
    • Pharmaceuticals
    • Ceramics
    • Silk
    • Textiles
    • Production of pure chemicals
    • Insecticides
    • Sugar refining
    • Manufacture of explosives
    • Used by plants to grow
    • To replace amputated bone, or even promote bone growth on prosthetic implants.
    • We have a dietary need for fluorine, phosphorous and calcium
pink apatite pieces mounted on wood

Apatite. Bancroft, Ontario. University of Waterloo Earth Sciences Museum Collection.

Notable occurrences:

Apatite is widely distributed in all classes of rock –igneous, sedimentary and metamorphic. Large, well-formed crystals are, for the most part, limited to metamorphic rocks. Although it can be found in many localities worldwide, some notable occurrences include:

  • Durango, Mexico
  • Bancroft, Ontario
  • Germany
  • Russia

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