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Putnisite

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Putnisite
Putnisite, from Polar Bear Peninsula, Western Australia, Australia
General
CategoryMineral
Formula
(repeating unit)		SrCa4Cr8(CO3)8(SO4)(OH)16·25 H2O
IMA symbolPni
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space groupPnma
Unit cella = 15.351 Å,
b = 20.421 Å,
c = 18.270 Å; Z = 4
Identification
ColorPurple
Crystal habitPseudocubic crystals
Cleavage, and good
FractureBrittle – uneven
Mohs scale hardness1.5–2
LusterVitreous
StreakPink
DiaphaneityTranslucent
Specific gravity2.20
Optical propertiesBiaxial (−)
Refractive indexnα = 1.552, nβ = 1.583 and nγ = 1.599
PleochroismDistinct: X pale bluish grey, Y pale purple, Z pale purple
References

Putnisite is a mineral composed of strontium, calcium, chromium, sulfur, carbon, oxygen and hydrogen. It was discovered on the Polar Bear Peninsula in Shire of Dundas, Western Australia in 2007 during mining activity. Following identification and recognition by the IMA in 2012 the mineral was named after mineralogists Andrew and Christine Putnis.

Putnisite has unique chemical and structural properties, and does not appear to be related to any of the existing mineralogical families. Crystals are translucent purple, but show distinct pleochroism (from pale purple to pale bluish grey, depending on the angle of observation) and leave pink streaks when rubbed on a flat surface.

Putnisite occurs as small (< 0.5 mm) cube-like crystals in volcanic rock. The mineral formed during the oxidation environment within komatiite to dioritic bodies containing sulfide minerals.

References

  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. Mineralienatlas
  3. ^ "New Mineral Shows Nature's Infinite Variability". University of Adelaide. Retrieved 26 April 2014.
  4. ^ Elliott, P. (February 2014). "Putnisite". Mineralogical Magazine. 78 (1): 131–144. doi:10.1180/minmag.2014.078.1.10. S2CID 102242056. Retrieved 26 April 2014.
  5. ^ "Putnisite: Putnisite mineral information and data". Mindat.org. 2014-04-07. Retrieved 2014-04-29.


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