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Chemical composition Ca5(PO4)3(F,Cl,OH)
Crystal system Hexagonal
Habit Prismatic
Cleavage Imperfect, basal
Fracture Conchoidal
Hardness 5
Optic nature Uniaxial -
Refractive index 1.63-1.64
Birefringence 0.003
Dispersion Low, 0.013
Specific gravity 3.2
Lustre Vitreous
Pleochroism Weak

Faceted Apatite
Photo courtesy of The Gem Trader
Unusual Violet Faceted Apatite
Photo courtesy of Jason Brim

Apatite is named "the deceiver" as it's color, refractometer and specific gravity readings are similar to gemstones as tourmaline, topaz, andalusite and danburite.



Apatite occurs in yellow, green, violet, purple, blue, brown, colorless and pink and can be transparent to translucent.

Optic Character

DR, Uniaxial negative


Refractometer readings are in the range of tourmaline, topaz, andalusite and danburite but usually with a very low birefringence of 0.003.
Full range: nω = 1.629 - 1.667 and nε = 1.624 - 1.666 with a full birefringence of 0.001-0.007.


The spectroscope is a good diagnostic tool in seperating apatite from gemstones as tourmaline and topaz.

Blue apatite will, usually, show a rare earth spectrum line in the blue (praseodymium).
Blue-green stones may have added spectrum lines in the yellow (didymium) and line(s) in the green (praseodymium).
Yellow gems show the rare earth spectrum of greenish-blue without the line in the blue.
Neon blue stones may show rare earth spectra in the yellow.

UV Reactions

  • Blue: Blue to light blue (LW and SW)
  • Yellow: Purplish Pink (stronger in LW)
  • Green: Greenish-yellow (stronger in LW)
  • Violet: Greenish-yellow (LW);Light purple (SW)

Chelsea Colour Filter

Green-blue stones: green


Apatite has weak pleochroism, so this tool may not be very useful except for blue stones where the dichroism is more profound (blue and pale yellow).


A nice uniaxial negative interference figure should be found.

Primary Sources

Brazil, Burma, Mexico
Violet and Purple are found in Maine and Afghanistan.


Clouds of tiny white crystal inclusions may be easily observed.

Blue apatite with crystalline "fireworks" of an unidentified mineral
40X Magnification
by Barbra Voltaire
Yellow apatite with a 3-dimensional network of liquid needles
40X Magnification
by Barbra Voltaire


  • Cat's-eyes

G&G Articles on Apatite 1934-1980

The GIA has published all the G&G's from 1934 until 1980 online. The organization of the list by subject was done by Joseph Gill.