Marshite

Marshite
Exceptionally well crystallized specimen of the rare copper iodide marshite from the Rubtsovskoe Deposit, Altaiskii Krai, Western Siberia, Russian Federation.
General
CategoryHalide mineral
Formula
(repeating unit)
CuI
IMA symbolMsh[1]
Strunz classification3.AA.05
Dana classification9.1.7.3
Crystal systemIsometric
Crystal classHextetrahedral (43m)
Space groupF43m
Unit cella = 6.05 Å (untwinned a = 6.6063(1) Å); Z=4
Identification
ColorHoney-yellow, exposed to air pink-red to brick-red
Crystal habitTetrahedral crystals, cubo-octahedral, crusts
TwinningOn {111}
Cleavage{011} perfect
FractureConchoidal
TenacityBrittle
Mohs scale hardness2.5
LusterAdamantine, greasy
StreakYellow
DiaphaneityTransparent
Specific gravity5.68
Density5.68 g/cm3 (measured),
5.71 g/cm3 (calculated)
Optical propertiesIsotropic
Ultraviolet fluorescenceDark red (SW, LW)
References[2][3][4][5]

Marshite (CuI) is a naturally occurring isometric halide mineral with occasional silver (Ag) substitution for copper (Cu).[6][7] Solid solution between the silver end-member miersite and the copper end-member marshite has been found in these minerals from deposits in Broken Hill, Australia.[8] The mineral's name is derived from the person who first described it, an Australian mineral collector named Charles W. Marsh.[2][3][4] Marsh drew attention to native copper iodide (Marshite) in the 1800s emphasizing its natural occurrence, it is not to be confused with copper (I) iodide a substance commonly synthesized in laboratory settings.[9][10]

One of marshite's distinguishing features is that prior to exposure to air the mineral is a faint honey-yellow color, once exposed to the air however it becomes a brick-red color.[2][3] Another characteristic useful in identifying marshite is the dark red color it fluoresces under short-wave (SW) and long-wave (LW) ultraviolet light.[2][4]

  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 c d Handbook of Mineralogy - Marshite
  3. ^ a b c Mindat.org - Marshite
  4. ^ a b c Webmineral - Marshite
  5. ^ Cooper, M.A., and Hawthorne, F.C. (1997) “A note on the crystal structure of marshite”, The Canadian Mineralogist, 35: 785–786.
  6. ^ Prior, G.T. (1902) “The identity of kilbrickenite with geocronite: And analyses of miersite, marshite, and copper-pyrites”, Mineralogical Magazine, 13: 186–190.
  7. ^ Palache, C., Berman, H., Frondel, C. (1951) "The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana Yale University 1837-1892, Volume II: Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphates, Arsenates, Tungstates, Molybdates, Etc." John Wiley and Sons, Inc., New York, 7th edition, revised and enlarged: pp. 20-22.
  8. ^ Millsteed, P.W. (1998) “Marshite - miersite solid solution and iodargyrite from Broken Hill, New South Wales, Australia“. Mineralogical Magazine, 62(4): 471–475.
  9. ^ Marsh, C.W. (1892) Proceedings of the Royal Society of New South Wales, 26: 326–332 (as Native copper iodide).
  10. ^ Marsh, C.W. and Liversidge, A. (1892) "On Native Copper Iodide (Marshite) and other Minerals from Broken Hill, N.S. Wales", Journal and Proceedings of the Royal Society of New South Wales, 26: 326–332.