brushite
{{Short description|Calcium phosphate mineral}}
{{Distinguish|Brucite|Magnesium hydroxide}}
{{Infobox mineral
| image = Brushite, Montmorillonite-445846.jpg
| caption = Brushite (white) on montmorillonite
| name = Brushite
| category = Phosphate mineral
| formula = {{chem2|CaHPO4 * 2 H2O}}
| strunz = 8.CJ.50
| system = Monoclinic
| symmetry = Ia (no. 9)
| unit cell = a = 6.265 Å, b = 15.19 Å,
c = 5.814 Å; β = 116.47°; Z = 4
| color = Colorless to pale or ivory-yellow
| habit = Prismatic to tabular acicular crystals; typically powdery or earthy
| twinning =
| cleavage = Perfect on {010} and {001}
| fracture =
| tenacity = Brittle
| mohs = 2.5
| luster = Vitreous, pearly on cleavages
| streak =
| diaphaneity = Transparent to translucent
| gravity = 2.328
| density =
| polish =
| opticalprop = Biaxial (+)
| refractive = nα = 1.539 – 1.540
nβ = 1.544 – 1.546
nγ = 1.551 – 1.552
| birefringence = δ = 0.012
| pleochroism =
| 2V = Measured: 59 to 87°
| dispersion =
| extinction =
| length fast/slow =
| fluorescence =
| absorption =
| melt =
| fusibility =
| diagnostic =
| solubility = Readily in HCl
| impurities =
| alteration =
| other = Piezoelectric
| prop1 =
| prop1text =
| references = {{cite book|editor1-last=Anthony|editor1-first=John W.|editor2-last=Bideaux|editor2-first=Richard A.|editor3-last=Bladh|editor3-first=Kenneth W.|editor4-last=Nichols|editor4-first=Monte C.|title= Handbook of Mineralogy|publisher=Mineralogical Society of America|place=Chantilly, VA, US|url=http://www.handbookofmineralogy.com/pdfs/brushite.pdf |chapter=Brushite|isbn=0962209732 |volume=IV (Arsenates, Phosphates, Vanadates)|year=2000|archive-url=https://web.archive.org/web/20160304052347/http://www.handbookofmineralogy.com/pdfs/brushite.pdf|archive-date=2016-03-04}}[https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Brushite Brushite]. Mineralienatlas][http://www.mindat.org/min-793.html Brushite]. Mindat.org{{cite journal |last1=Schofield |first1=P. F. |last2=Knight |first2=K. S. |last3=Houwen |first3=J. A. M. van der |last4=Valsami-Jones |first4=E. |title=The role of hydrogen bonding in the thermal expansion and dehydration of brushite, di-calcium phosphate dihydrate |journal=Physics and Chemistry of Minerals |date=December 2004 |volume=31 |issue=9 |pages=606–624 |doi=10.1007/s00269-004-0419-6|bibcode=2004PCM....31..606S |s2cid=94011250 }}
}}
Brushite is a phosphate mineral with the chemical formula {{chem2|CaHPO4*2H2O}}. Crystals of the pure compound belong to the monoclinic space group C2/c and are colorless.[http://webmineral.com/data/Brushite.shtml Brishite]. Webmineral It is the phosphate analogue of the arsenate pharmacolite.
Discovery and occurrence
Brushite was first described in 1865 as an occurrence on Aves Island, Nueva Esparta, Venezuela, and named for the American mineralogist George Jarvis Brush (1831–1912). 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 the runoff of fields which have received heavy fertilizer applications. Associated minerals include tanarakite, ardealite, hydroxylapatite, variscite and gypsum.
Brushite is the original precipitating material in calcium phosphate kidney stones.{{cite web|title=Brushite|url=https://virtual-museum.soils.wisc.edu/display/brushite/|website=Virtual Museum of Molecules and Minerals|accessdate=22 December 2017}} It is also one of the minerals present in dental calculi.
References
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