Chemistry:Whiteite

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Whiteite
Whiteite-Lazulite-48334.jpg
Whiteite with lazulite from Rapid Creek, Dawson Mining District, the Yukon, Canada
General
CategoryPhosphate minerals
Formula
(repeating unit)		Whiteite-(CaFeMg):

CaFe2+Mg2Al2(PO4)4(OH)2·8H2O
Whiteite-(MnFeMg):
Mn2+Fe2+Mg2Al2(PO4)4(OH)2·8H2O
Whiteite-(CaMnMg):

CaMn2+Mg2Al2(PO4)4(OH)2·8H2O
Strunz classification8.DH.15 (10 ed, whole series)
7/D.29 (8 ed)
Dana classification42.11.3.1 Whiteite-(CaFeMg)

42.11.3.2 Whiteite-(MnFeMg)

42.11.3.3 Whiteite-(CaMnMg)
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupP2/a (no. 13)
Identification
Formula massWhiteite-(CaFeMg):756.29g

Whiteite-(MnFeMg):767.44g

Whiteite-(CaMnMg):755.61g
ColorWhiteite-(CaFeMg): Brown, pink-brown or yellow

Whiteite-(MnFeMg): Brown

Whiteite-(CaMnMg): Yellow, light lavender or pink
Crystal habitTabular crystals or aggregates thereof
TwinningInvariably twinned by reflection on {001} producing a pseudo-orthorhombic appearance
CleavageOn {001}. Poor for whiteite-(CaMnMg), but good for the other members of the series (HOM)
TenacityWhiteite-(CaMnMg) is brittle (HOM)
Mohs scale hardness3 to 4
|re|er}}Vitreous
StreakWhite to brownish white
DiaphaneityTranslucent to transparent
Specific gravityWhiteite-(CaFeMg) 2.58

Whiteite-(MnFeMg)2.67

Whiteite-(CaMnMg)2.63
Optical propertiesBiaxial (+)
Refractive indexNx = 1.580, Ny = 1.584 to 1.585, Nz = 1.590 to 1.591
Other characteristicsNot radioactive
References[1][2][3][4][5][6][7][8][9]

Whiteite is a rare hydrated hydroxyphosphate mineral.

Whiteite subgroup

The name whiteite refers to three minerals in the jahnsite-whiteite group, whiteite subgroup. Subgroup members (formulae from IMA[8]):

  • Whiteite-(CaFeMg), IMA1975-001, CaFe2+Mg2Al2(PO4)4(OH)2·8H2O
  • Whiteite-(MnFeMg), IMA1978-A, Mn2+Fe2+Mg2Al2(PO4)4(OH)2·8H2O
  • Whiteite-(CaMnMg), IMA1986-012, CaMn2+Mg2Al2(PO4)4(OH)2·8H2O
  • Rittmannite, Mn2+Mn2+Fe2+2Al2(PO4)4(OH)2·8H2O

In the whiteite formulae, the symbols in brackets indicate the dominant atom in three distinct structural positions, designated X, M(1), and M(2), in that order; for instance, magnesium Mg is always the dominant atom in the M(2) position for all the whiteite minerals.[5] Whiteite was named after John Sampson White Jr (born 1933),[10] associate curator of minerals at the Smithsonian Institution, and founder, editor and publisher (1970–1982) of the Mineralogical Record.[11]

Unit cell

All members of the series belong to the monoclinic crystal system with point group 2/m. Most sources give the space group as P21/a for the Ca Fe rich member, which was the first of the series to be described,[6][2][5] but Dana gives it as P2/a.[1] The other members are variously described in different sources as having space groups P21/a, P2/a or Pa.

There are two formula units per unit cell (Z = 2). The cell parameters vary slightly between the group members, but to the nearest angstrom they all have a = 15 Å, b = 7 Å and c = 10 Å, with β 112.5 to 113.4. Individual values are:[1][2][3][4][5][6]

  • Whiteite-(CaFeMg) a = 14.90 Å, b = 6.98 Å, c = 10.13 Å, β = 113.12
  • Whiteite-(MnFeMg) a = 14.99 Å, b = 6.96 Å, c = 10.14 Å, β = 113.32
  • Whiteite-(CaMnMg) a = 14.842 Å, b = 6.976 Å, c = 10.109 Å, β = 112.59

Appearance

The whiteite minerals are generally brown, pink or yellow, and whiteite-(CaMnMg) may also be light lavender coloured.[5] They are transparent to translucent, with a vitreous luster and a white to brownish white streak. They occur as aggregates of tabular crystals, or thick tabular canoe-shaped crystals.[1] Whiteite from Rapid Creek in the Yukon, Canada, is often associated with deep blue lazulite crystals (33 out of 49 photos on Mindat.org).

Optical properties

The optical class is thought to be biaxial (+),[7][2][3][4] but whiteite-(CaFeMg) may be biaxial (−).[5][6] The refractive indices are Nx = 1.580, Ny = 1.584 to 1.585 and Nz = 1.590 to 1.591, similar to those for quartz.

Physical properties

Whiteite is invariably twinned, giving the crystals a pseudo-orthorhombic appearance,[1][5] and the cleavage is good to perfect.[5] Whiteite is quite soft, with hardness 3 to 4, between calcite and fluorite. Its specific gravity is 2.58, similar to that of quartz.[1][2][3][4][5][6] Whiteite is not radioactive.[2][3][4]

Occurrence

The type locality for whiteite-(CaFeMg)and whiteite-(MnFeMg) is the Ilha claim, Taquaral, Itinga, Jequitinhonha valley, Minas Gerais, Brazil, and for whiteite-(CaMnMg) it is the Tip Top Mine (Tip Top pegmatite), Fourmile, Custer District, Custer County, South Dakota, US.[7] The type material is conserved at the National School of Mines, Paris, France, and at the National Museum of Natural History, Washington DC, US, reference 123013.[5]

At the Lavra da Ilha pegmatite, Taquaral, Brazil, whiteite is found in a complex zoned granite pegmatite associated with eosphorite, zanazziite, wardite, albite and quartz.[5] At Blow River, the Yukon, Canada, it is found in iron-rich sedimentary rocks with siderite, lazulite, arrojadite and quartz.[5] At Ilha de Taquaral, Minas Gerais, Brazil, it occurs along joints and fractures in quartz and albite associated with other phosphates.[6]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Gaines et al (1997) Dana's New Mineralogy Eighth Edition. Wiley
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 "Whiteite-(CaFeMg) Mineral Data". Webmineral.com. http://www.webmineral.com/data/Whiteite-(CaFeMg).shtml. Retrieved 2012-03-15. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 "Whiteite-(MnFeMg) Mineral Data". Webmineral.com. http://www.webmineral.com/data/Whiteite-(MnFeMg).shtml. Retrieved 2012-03-15. 
  4. ↑ 4.0 4.1 4.2 4.3 4.4 "Whiteite-(CaMnMg) Mineral Data". Webmineral.com. http://www.webmineral.com/data/Whiteite-(CaMnMg).shtml. Retrieved 2012-03-15. 
  5. ↑ 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 5.09 5.10 5.11 "Handbook of Mineralogy". Handbook of Mineralogy. http://www.handbookofmineralogy.org. Retrieved 2012-03-15. 
  6. ↑ 6.0 6.1 6.2 6.3 6.4 6.5 Fleischer, Chao and Pabst (1979) American Mineralogist 64:465, summarising Moore and Ito (1978) Mineralogical Magazine 42:309 [Whiteite-(CaMnMg) – AM75: Jambor and Grew (1990) American Mineralogist 75:933, summarising Grice, Dunn and Ramik (1989) The Canadian Mineralogist 27:699]
  7. ↑ 7.0 7.1 7.2 "Whiteite-(CaFeMg): Whiteite-(CaFeMg) mineral information and data". Mindat.org. 2012-01-30. http://www.mindat.org/min-4277.html. Retrieved 2012-03-15. 
  8. ↑ 8.0 8.1 "IMA Mineral List with Database of Mineral Properties". Rruff.info. http://rruff.info/ima. Retrieved 2012-03-15. 
  9. ↑ Elliott, Peter; Willis, Anthony C. (1 March 2019). "Whiteite-(mnmnmg), a New Jahnsite-Group Mineral from Iron Monarch, South Australia: Description and Crystal Structure". The Canadian Mineralogist 57 (2): 215–223. doi:10.3749/canmin.1800070. 
  10. ↑ "Label Archive". The Mineralogical Record. 1933-09-30. http://www.mineralogicalrecord.com/labels.asp?colid=606. Retrieved 2012-03-15. 
  11. ↑ "The Mineralogical Record". The Mineralogical Record. http://www.mineralogicalrecord.com. Retrieved 2012-03-15. 



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