Mineral Information and Data:

Chlorapatite
Ca5(PO4)3Cl [CNMNC approved formula]

Named from the Greek apatao - "I am misleading". Named in 1860 as apatite, then renamed to apatite-(CaCl) in 2008, and reversed renamed in 2010 as the chlorine end-member.

IMA status : Renamed IMA Approved; 2010 ()
CLASSIFICATION 
Dana
(8th edition) :
41.08.01.02  
  (41) Anhydrous Phosphates Containing Hydroxyl or Halogen
  (41.08) where (A)5 (XO4)3 Zq
  (41.08.01) Apatite Group
  
Nickel-Strunz
(10th edition) :
08.BN.05
  (08) Phosphates, Arsenates, Vanadates
  (08.B) Phosphates, etc. with Additional Anions, without H2O
  (08.BN) With only large cations, (OH, etc.):RO4 = 0.33:1
  
Crystal system: Hexagonal System
Point group (H-M): 6/m — dipyramidal
Unit cell: a = 9.5979Å, c = 6.7762Å
Crystal Habit: As prismatic hexagonal crystals, to 5 cm; granular, massive, may be in zoned intergrowths with fluorapatite.
  
Color: Greenish yellow, pinkish white, light greenish gray
Diaphaneity: Transparent to translucent
Luster: Vitreous
Hardness (Mohs): 5
Measured Density: 3.1 to 3.2 g/cm3
Cleavage: 2; poor on {0001} and {1010} trance
Tenacity: Brittle
  
Geologic Setting: Relatively much rarer than fluorapatite or hydroxylapatite, formed in F-deficient environments. In calcsilicate marble; an accessory mineral in layered mafic intrusions; in veins through diabase; replacing triphylite in granite pegmatite. In meteorites.
Mineral Association: Actinolite, diopside, calcite, quartz, talc (Bob’s Lake, Canada); amphibole, chlorite, plagioclase, titanite, datolite (Bull Run quarry, Virginia, USA); olivine, orthopyroxene, phlogopite, ferroalluaudite, chromite (Angarf-Sud pegmatite, Morocco
  
Synonyms/varieties: Apatite-(CaCl)
Other Properties: BioMineral.
Comments: Chlorapatite - Renamed to apatite-(CaCl) by Mineralogical Record, v39 (2008), p 131. However, it was reversed back to chlorapatite in 2010. The monoclinic variant is defined as chlorapatite-M and is not a distinct species:
Pasero M, Kampf A R, Ferraris C, Pekov I V, Rakovan J R, White T J (2010) Nomenclature of the apatite supergroup minerals, European Journal of Mineralogy 22, 163-179

 

Chlorapatite
Green crystalline 5 mm large apatite in quartz matrix; analysed material
Origin: Horni slavkov, Bohemia, Czech Republic
Sample size: 2 x 4 cm
Photo: Diederik Visser

 

Chlorapatite
Greenish Chlorapatite crystals with chlorite
Origin: Kurokura, Kanagawa Pref., Honshu Island, Japan
Sample size: 2.2 x 2.1 x 1.9 cm
Photo: Rob Lavinsky

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