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Miguelromeroite

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Miguelromeroite
General
CategoryMineral
Formula
(repeating unit)
MnS(AsO4)2(HAsO4)2 · 4H2O
IMA symbolMig[1]
Crystal systemMonoclinic
Crystal classPrismatic
H-M symbol: 2/m
Space groupB2/b
Unit cell1,624.38
Identification
ColorSalmon pink to orange
TwinningNone observed
CleavageGood on {100}
FractureConchoidal
Mohs scale hardness4
LusterVitreous
StreakPale pink
DiaphaneityTransparent
Density3.69
Optical propertiesBiaxial (−)
Refractive indexnα = 1.713
nβ = 1.723
nγ = 1.729
Birefringence0.016
PleochroismVisible
2V angleMeasured: 70°
Calculated: 75°

Miguelromeroite is a mineral named for Miguel Romero Sanchez by Anthony Robert Kampf. The mineral, first described in 2008[2] was named in 2009, the same year it got approved by the International Mineralogical Association.

Properties

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Miguelromeroite is a member of the hureaulite group, and is the magnesium analogue of the mineral sainfeldite. It is known as a synthetic compound,[3] and was originally labeled as villyaellenite due to the very rare complex arsenate microcrystals.[2] It shows pleochroic attributes, which is an optical phenomenon that makes gems to be seen a different color depending on the axis it is being inspected. Viewing it from the Z axis, the mineral can be seen in a pale pink color. It was redefined as an intermediate species of the series. It is the full magnesium endmember of the series. Crystals are up to 4 cms in length, and are elongated on [001] with forms {100}, {110} and {101̅}.[4]

Structure

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The mineral's structure is defined by an octahedral edge-sharing pentamer. The pentamers are linked into a loose framework by sharing corners with octahedra in adjacent pentamers and they are further linked through AsO4 and AsO3OH tetrahedra. There are three distinct octahedral sites: M1, M2, and M3. In miguelromeroite's structure, all of the octahedral sites are occupied by magnesium and the average bond lengths for the sites fall within a relatively narrow range. Though the differences in the sites suggest that the sites M2 and M3 contain small amounts of zinc and calcium.[4]

Mines

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The samples were from the Veta Negra mine in Chile. Other mines include Gozaisho mine in Honshu island, Japan, and Mina Ojuela in Mapimi, Durango, Mexico. It's a type locality only in these three mines.[3]

References

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  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 Minerals, Dakota Matrix. "Miguelromeroite mineral information and data". www.dakotamatrix.com. Retrieved 2021-08-09.
  3. ^ a b "Miguelromeroite". www.mindat.org. Retrieved 2021-08-09.
  4. ^ a b R. Kampf, Anthony (2009). "Miguelromeroite, the Mn analogue of sainfeldite, and redefinition of villyaellenite as an ordered intermediate in the sainfeldite-miguelromeroite series" (PDF). American Mineralogist. 94 (11–12): 1535–1540. Bibcode:2009AmMin..94.1535K. doi:10.2138/am.2009.3278. S2CID 97734557.