Tlapallite

Tlapallite is a rare and complex tellurate mineral with the formula (Ca,Pb)3CaCu6[Te4+3Te6+O12]2(Te4+O3)2(SO4)2 · 3 H2O. It has a Moh's hardness of 3 and it is green in colour. It was named after the Nahua word "Tlalpalli", which translates to paint, referring to the paint-like habit of the mineral.[1] It has no uses beyond being a collector's item.

Tlapallite
Tlapallite on matrix from Bambollita mine (La Oriental), Moctezuma, Municipio de Moctezuma, Sonora, Mexico. Picture width: 29 mm
General
CategoryTellurate minerals
Formula
(repeating unit)
(Ca,Pb)3CaCu6[Te4+3Te6+O12]2(Te4+O3)2(SO4)2 · 3 H2O
Strunz classification4.JL.25
Dana classification34.8.2.1
Crystal systemMonoclinic
P3 2 1
Unit cella = 11.97 Å , b = 9.11 Å
c = 15.66 Å; Z = 4
Identification
ColorGreen
Crystal habitThin crusts or botryoidal aggregates
CleavageNone
Mohs scale hardness3
LusterVitreous, Waxy
StreakPale green
DiaphaneityTranslucent
Specific gravity5.38 (measured) 5.05-5.465 (calculated)
Optical propertiesBiaxial (-)
Refractive indexnα = 1.815 - 1.915 nβ = 1.960 - 2.115 nγ = 1.960 - 2.115
Birefringenceδ = 0.1450-0.2000
PleochroismModerate, different shades of green
2V angle0
Ultraviolet fluorescenceNone
FusibilityFuses readily
Diagnostic featuresThin green paint-like crusts
SolubilitySoluble in cold HCl
Slightly soluble in HNO3 unless heated
References

Occurrence

It was discovered in 1972 the Bambollita mine (La Oriental), Moctezuma, Municipio de Moctezuma, Sonora, Mexico, a mine known for its tellurium deposits, and it was approved by the IMA in 1977. Here, it is found as thin paint-like crusts on rock fractures and next to thin veins running through rhyolite. It is often found as a thin film on quartz, sericite, calcite or baryte, but it also forms botryoidal aggregates. It is often found alone, but may be associated with other minerals, especially carlfriesite.[2] It has also been found in the emerald mine in Tombstone District, Cochise County, Arizona in the United States.[1][3][4]

The habit of the mineral suggests it precipitates from rapidly drying acid solutions. It seems to form in the transitory phase when other tellurium minerals, like tlalocite, cesbronite, xocomecatlite, quetzalcoatlite, teineite and carlfriesite, start to break down.[2]

See also

References

  1. "Tlapallite: Tlapallite mineral information and data". www.mindat.org. Retrieved 2016-09-15.
  2. S.A. Williams and Marjorie Duggan (June 1978). "Tlapallite, a new mineral from Moctezuma, Sonora, Mexico" (PDF). Mineralogical Magazine. 42 (322): 183–186. CiteSeerX 10.1.1.615.5877. doi:10.1180/minmag.1978.042.322.03.
  3. Barthelmy, Dave. "Tlapallite Mineral Data". www.webmineral.com. Retrieved 2016-09-15.
  4. "Handbook of Mineralogy" (PDF).


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