Mineral phase
IMA name
Apatite-(CaOH)
Secondary names
Hydroxyapatite; Hydroxylapatite
Type
Class
non-silicate mineral
Compound type
phosphate
Chemical composition
Formula
$Ca_5(PO_4)_3(OH)$
Chemical formula
Ca5(PO4)3(OH)
Elemental formula
(Ca2+)5 P3 O3 (O-)10 H
Isotope mixture type
terrestrial abundance
  Formula Name Family Number min-max Isotope mole fraction State Relevance
$Ca^{2+}$ Calcium cation element 5 constituent cation main
$(PO_4)^{3-}$ Phosphate anion chemical function 3 anionic radical main
$(OH)^-$ Hydroxide anion chemical function 1 anionic radical main
Chemical functions
  Function Number
$(OH)^-$ 1
Chemical bonds
  Bond Number
$\cdot Ca^{2+} \cdot O^{-}-$ 10
$O^--H$ 1
Oxides
Formula $CaO$ $P_{2}O_{5}$ $H_{2}O$
Mass fraction (%) 55.82 42.39 1.79

Strunz

Class
phosphates - arsenates - vanadates (08)
Division
phosphates, etc. with additional anions, without H2O (08.B)
Family
with only large cations, (OH, etc.):RO4 = 0.33:1 (08.BN)
Code
08.BN.05

Dana

Major class
phosphates, arsenates, vanadates (VII)
Class
anhydrous phosphates containing hydroxyl or halogen (41)
Type
where (A)5 (XO4)3 Zq (41.08)
Group
Apatite group (41.08.01)
Code
41.08.01.03
Phase type
crystalline
Crystal system
hexagonal
Crystal class
dipyramidal
Crystal class symbol
6/m (C6h)
Crystal spacegroup
P6(3)/m
Molar mass
502.31 $g/mol$
Density
3.14-3.21 (calc.: 3.16) $g/cm^3$
State NTP
solid
Refringence type
uniaxial
Refringence sign
negative
Birefringence
0.0070
Refraction index $n_o$ (w)
1.651
Refraction index $n_e$ (e)
1.644
Pure color
colorless
Color
colorless, white, gray, yellow, yellowish green
Diaphaneity
transparent to opaque
Luster
vitreous
Links