Hureaulite
{{short description|Manganese phosphate mineral}}
{{Infobox mineral
|boxbgcolor=#d0a280| name = Hureaulite
| category = Phosphate minerals
| image = hureaulite 01.jpg
| imagesize = 260px
| caption = Hureaulite from the Cigana Claim, Conselheiro Pena, Minas Gerais, Brazil. Specimen size 2.8 cm.
| formula = {{chem2|Mn(2+)5(PO3OH)2(PO4)2*4H2O}}
| molweight = 728.65 g/mol
| strunz = 8.CB.10 (10 ed)
7/C.04-10 (8 ed)
| dana = 39.2.1.1
| system = Monoclinic
| class = Prismatic (2/m)
(same H-M symbol)
| symmetry = C2/c
| unit cell = a = 17.594(10) Å
b = 9.086(5) Å
c = 9.404(5) Å
β = 96.67(8)°; Z = 4
| colour = Orange, red, yellow, brown, grey or nearly colourless
| habit = Crystals are short prismatic parallel to (100) or equant, sometimes thick tabular, also massive or imperfectly fibrousMurdoch, Joseph (1942) Contributions to the Crystallography of Hureaulite. American Mineralogist 27: 228
| twinning =
| cleavage = {100} good
| fracture = Uneven
| tenacity = Brittle
| mohs = 3.5
| lustre = Vitreous to greasy
| refractive = nα = 1.640 – 1.654 nβ = 1.649 – 1.659 nγ = 1.655 – 1.662
| opticalprop = Biaxial (−)
| 2V = greater than 60°
| dispersion = r
| birefringence = δ = 0.012
| pleochroism = X colourless, Y yellow to pale rose, Z reddish yellow to reddish brown
| streak = Nearly white
| gravity = 3.18–3.2 (measured), 3.23 (calculated)
| density =
| melt =
| fusibility =
| diagnostic =
| solubility = Easily soluble in acids.
| diaphaneity = Transparent to translucent
| other =
| references = Gaines et al (1997) Dana's New Mineralogy Eighth Editionhttp://www.mindat.org/min-1952.html Mindat.orgShigley and Brown (1985) American Mineralogist 70:395Roberts, Campbell and Rapp (1990) Encyclopedia of Minerals, 2nd edition}}
Hureaulite is a manganese phosphate with the formula {{chem2|Mn(2+)5(PO3OH)2(PO4)2*4H2O}}. It was discovered in 1825 and named in 1826 for the type locality, Les Hureaux, Saint-Sylvestre, Haute-Vienne, Limousin, France. It is sometimes written as huréaulite, but the IMA does not recommend this for English language text.Burke, E. A. J. (2008): Tidying up Mineral Names: An IMA scheme for Suffixes, Hyphens and Diacritical Marks. Mineralogical Record, 39, 134
A complete series exists from lithiophilite, {{chem2|LiMn(2+)PO4}} to triphylite, {{chem2|LiFe(2+)PO4}}, including hureaulite, strengite, {{chem2|FePO4*2H2O}}, stewartite, {{chem2|Mn(2+)Fe(3+)2(OH,PO4)2*8H2O}}, and sicklerite, {{chem2|(LiMn(2+),Fe(3+))PO4}}.Murdoch, Joseph (1943) Crystallography of Hureaulite. American Mineralogist 28: 19-24
Environment
Hureaulite is a secondary mineral occurring in granite pegmatites. At the type locality it occurs in a zone of altered triphylite, {{chem2|LiMn(2+)PO4}}, in pegmatite. Typically occurs very late in the sequence of formation of secondary phosphate minerals.Moore, P B, and Araki, T (1973) Hureaulite: its atomic arrangement. American Mineralogist 58: 302-307. Associated at the type locality with vivianite, {{chem2|Fe(2+)3(PO4)2*8H2O}}; rockbridgeite, {{chem2|Fe(2+)Fe(3+)4(PO4)3(OH)5}}; heterosite, {{chem2|(Fe(3+),Mn(3+))PO4}} and cacoxenite, {{chem2|Fe(3+)24AlO6(PO4)17(OH)12*17H2O}}. It can be synthesised;Gerault, Y, Riou, A, and Cudennec, Y (1987) Acta Crystallographica (C) 43:1829 most natural hureaulites are Mn-rich compounds but extensive ({{chem2|Mn,Fe}}) solution is known for synthetic material.
Localities
The type locality is Les Hureaux, Saint-Sylvestre, Haute-Vienne, Limousin, France. Hureaulite is also found in a granite pegmatite known for its phosphates in the Aimorés pegmatite district, at the Cigana claim in Galiléia, Doce valley, Minas Gerais, Brazil, formerly known as the Jocão Mine.