Apatite

1. Chemical Composition Calcium phosphate with some chlorine or fluorine. Ca(F,Cl)Ca4(PO4)3
2. Classification / Type -
3. Colors / Varieties All colors. Chatoyant variety is very common.
4. Crystal System / Forms Hexagonal System / Generally as six sided prisms with pyramidal and / or pinacoidal terminations, commonly as contact twins.
5. Hardness 5
6. Specific Gravity 3.15 - 3.23
7. Cleavage / Fracture 2 directional basal and prismatic cleavage / conchoidal fracture
8. Optic Character Anisotropic, D.R.; Uniaxial negative (pseudo biaxial optic figure possible).
9. Lustre Vitreous.
10. Refractive Index / Birefringence 1.642 - 1.646 / 0.002 - 0.006. Range: 1.637 - 1.651
11. Pleochroism Weak, except in Burmese (Myanmar) gemstones.
12. Dispersion 0.013
13. Magnification Fibrous inclusions, parallel black needles or canals, liquid fingerprints, phase inclusions and crystals.
14. U.V. Fluorescence Varies according to color under ultra violet light.
15. Cause of Color
  • Yello green - rare earth elements
  • Blue - manganese.
16. Spectrum Generally, a series of lines at around 580nm and 520nm in the yellow-green, with other lines at 512nm, 491nm and 464nm may be seen. Rare earth didymium spectrum composed of mainly the elements praseodymium and neodymium. Blue apatite may not show spectrum, sometimes.
17. Treatment (Enhancement) -
18. Specific Tests & Remarks
  • Attacked by hydrochloric and sulphuric acid.
  • Reacts to heat and may lose color.
19. Synthesis Synthesized for use in lasers but cut synthetics are not sold commercially.
20. Simulants (with key separation tests)
  • Transparent varieties can simulate a number of different gemstones with respect to their color.
  • Apatite cat's eye: Quartz (R.I., S.G., spectrum, inclusions), Chrysoberyl (R.I., S.G., spectrum, inclusions), Glass (inclusions), etc.
21. Geological Occurrence Found in pegmatite, hydrothermal veins and cavities, metamorphic rocks in gem gravels.
22. Sources Sri Lanka, Myanmar, Norway, Canada, India, Germany, Pakistan, Madagascar, Tanzania, Brazil.
23. Cuts & Uses Facetted cuts, cabochon, beads, carvings, etc.