Sturmanite

Sturmanite
Sturmanite
	Distinctive sturmanite on matrix from the N'Chwaning Mines. Size: 5.4 x 4.2 x 1.7 cm. Ex.Charlie Key Stock
General
Category	Sulfate minerals
Formula; (repeating unit)	Ca6Fe3+2(SO4)2.5[B(OH)4](OH)12 · 25 H2O
Strunz classification	7.DG.15
Dana classification	32.4.4.2
Crystal system	Trigonal
Crystal class	3m - Ditrigonal Pyramidal
Space group	P31c (no. 159)
Unit cell	a = 11.188(9) Å, c = 21.91(7) Å
Identification
Color	Bright yellow to amber
Crystal habit	Hexagonal, pyramidal, prismatic
Cleavage	Perfect {1010}
Tenacity	Brittle
Mohs scale hardness	2.5
Luster	Vitreous, greasy
Streak	Pale yellow, greenish yellow, brownish orange
Diaphaneity	Transparent to translucent
Specific gravity	1.847 (measured) 1.855 (calculated)
Optical properties	Uniaxial (+/-)
Birefringence	δ = 0.002
Ultraviolet fluorescence	none

Sturmanite is a rare sulfate mineral with the chemical formula Ca₆Fe³⁺₂(SO₄)_2.5(B(OH)₄)(OH)₁₂ · 25 H₂O.^[1]^[2]^[3] It crystallises in the tetragonal system and it has a Moh's hardness of 2.5. Sturmanite has a bright yellow to amber colour and falls in the ettringite group. It was named after Bozidar Darko Sturman (born 1937), Croatian-Canadian mineralogist and Curator Emeritus of Mineralogy, Royal Ontario Museum.^[4]

Occurrence[]

Sturmanite was first identified in 1983 and approved by the IMA in the same year.^[3]^[4] It was first found in the Black Rock Mine, Black Rock, Kalahari manganese field, Northern Cape Province, South Africa. It is found as flattened dipyramidal crystals on hematite and baryte.^[4] Sturmanite has also been identified in mines near the Black Rock Mine, such as the Wessel's and Perth mines, in the N'Chwaning mines, and near Lakargi Mountain in Russia.^[1] It is found as a rare secondary mineral embedded in manganese deposits and is associated with baryte, manganite, hausmannite, and hematite.^[2]

Crystal structure[]

The crystal structure of sturmanite shows two distinct features: one being columns of iron-octahedra and calcium polyhedra, the other being the SO₄⁻ and B(OH)₄⁻ tetrahedra surrounding these columns. These two structures are linked together through a dense and complex network of hydrogen bonds.^[5]

References[]

^ Jump up to: ^a ^b "Sturmanite: Sturmanite mineral information and data". www.mindat.org. Retrieved 2017-02-19.
^ Jump up to: ^a ^b "Sturmanite" (PDF). Handbook of mineralogy.
^ Jump up to: ^a ^b Barthelmy, Dave. "Sturmanite Mineral Data". www.webmineral.com. Retrieved 2017-02-19.
^ Jump up to: ^a ^b ^c Peacor, D.R., Dunn, P.J., Duggan, M. (1983). "Sturmanite, a ferric iron, boron analogue of ettringite". Canadian Mineralogist. 21: 705–709.CS1 maint: multiple names: authors list (link)
^ Pushcharovsky, D.Y., Lebedeva, Y.S., Zubkova, N.V., Pasero, M., Bellezza, M., Merlino, S., Chukanov, N.V. (2004). "The crystal structure of sturmanite" (PDF). The Canadian Mineralogist. 42 (3): 723–729. CiteSeerX 10.1.1.605.4915. doi:10.2113/gscanmin.42.3.723.CS1 maint: multiple names: authors list (link)

[:0-1] Jump up to: ^a ^b "Sturmanite: Sturmanite mineral information and data". www.mindat.org. Retrieved 2017-02-19.

[:2-2] Jump up to: ^a ^b "Sturmanite" (PDF). Handbook of mineralogy.

[:1-3] Jump up to: ^a ^b Barthelmy, Dave. "Sturmanite Mineral Data". www.webmineral.com. Retrieved 2017-02-19.

[:3-4] Jump up to: ^a ^b ^c Peacor, D.R., Dunn, P.J., Duggan, M. (1983). "Sturmanite, a ferric iron, boron analogue of ettringite". Canadian Mineralogist. 21: 705–709.CS1 maint: multiple names: authors list (link)

[5] Pushcharovsky, D.Y., Lebedeva, Y.S., Zubkova, N.V., Pasero, M., Bellezza, M., Merlino, S., Chukanov, N.V. (2004). "The crystal structure of sturmanite" (PDF). The Canadian Mineralogist. 42 (3): 723–729. CiteSeerX 10.1.1.605.4915. doi:10.2113/gscanmin.42.3.723.CS1 maint: multiple names: authors list (link)

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