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Brushite, Montmorillonite-445846.jpg
Brushite (white) on montmorillonite
CategoryPhosphate mineral
(repeating unit)
CaHPO4 · 2 H2O
IMA symbolBsh[1]
Strunz classification8.CJ.50
Crystal systemMonoclinic
Space groupIa (no. 9)
Unit cella = 6.265 Å, b = 15.19 Å,
c = 5.814 Å; β = 116.47°; Z = 4
ColorColorless to pale or ivory-yellow
Crystal habitPrismatic to tabular acicular crystals; typically powdery or earthy
CleavagePerfect on {010} and {001}
Mohs scale hardness2.5
LusterVitreous, pearly on cleavages
DiaphaneityTransparent to translucent
Specific gravity2.328
Optical propertiesBiaxial (+)
Refractive indexnα = 1.539 – 1.540
nβ = 1.544 – 1.546
nγ = 1.551 – 1.552
Birefringenceδ = 0.012
2V angleMeasured: 59 to 87°
SolubilityReadily in HCl
Other characteristicsPiezoelectric

Brushite is a phosphate mineral with the chemical formula CaHPO4·2H2O. Crystals of the pure compound belong to the monoclinic space group C2/c and are colorless.[2][5] It is the phosphate analogue of the arsenate pharmacolite.

Discovery and occurrence[edit]

Brushite was first described in 1865 for an occurrence on Aves Island, Nueva Esparta, Venezuela, and named for the American mineralogist George Jarvis Brush (1831–1912).[4] It is believed to be a precursor of apatite and is found in guano-rich caves, formed by the interaction of guano with calcite and clay at a low pH. It occurs in phosphorite deposits and forms encrustations on old bones. It may result from runoff of fields which have received heavy fertilizer applications.[4] Associated minerals include tanarakite, ardealite, hydroxylapatite, variscite and gypsum.[2]

Brushite is the original precipitating material in calcium phosphate kidney stones.[7] It is also one of the minerals present in dental calculi.


  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ a b c Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C., eds. (2000). "Brushite". Handbook of Mineralogy (PDF). Vol. IV (Arsenates, Phosphates, Vanadates). Chantilly, VA, US: Mineralogical Society of America. ISBN 0962209732. Archived from the original (PDF) on 2016-03-04.
  3. ^ Brushite. Mineralienatlas]
  4. ^ a b c Brushite.
  5. ^ a b Brishite. Webmineral
  6. ^ Schofield, P. F.; Knight, K. S.; Houwen, J. A. M. van der; Valsami-Jones, E. (December 2004). "The role of hydrogen bonding in the thermal expansion and dehydration of brushite, di-calcium phosphate dihydrate". Physics and Chemistry of Minerals. 31 (9): 606–624. Bibcode:2004PCM....31..606S. doi:10.1007/s00269-004-0419-6. S2CID 94011250.
  7. ^ "Brushite". Virtual Museum of Molecules and Minerals. Retrieved 22 December 2017.