Carlfriesite is a rare tellurium mineral with the formula CaTe4+2Te6+O8, or more simplified: CaTe3O8. It has a Moh's hardness of 3.5 and it occurs in various shades of yellow, ranging from bright yellow to a light buttery color. It was named after Carl Fries Jr. (1910–1965) from the U.S. Geological Survey and the Geological Institute of the National University, Mexico City, Mexico.[3][4][5] It was previously thought to have the formula H4Ca(TeO3)3, but this was proven to be incorrect.[6] It has no uses beyond being a collector's item.

Carlfriesite
Carlfriesite from Moctezuma Mine, Moctezuma, Municipio de Moctezuma, Sonora, Mexico. Picture width: 2 mm.
General
CategoryTellurate minerals
Formula
(repeating unit)
CaTe4+2Te6+O8
IMA symbolClf[1]
Strunz classification4.JK.25
Dana classification34.5.3.1
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupC2/c
Unit cella = 12.576, b = 5.662
c = 9.994 [Å], Z = 4
Identification
ColorBright yellow – buttery yellow
Crystal habitAxe-head shaped crystals, botryoidal crusts or radial crystals.
CleavageDistinct
TenacityBrittle
Mohs scale hardness3.5
LusterVitreous
StreakPale yellow
DiaphaneityTransparent
Specific gravity6.3 (measured) 5.7 (calculated)
Optical propertiesBiaxial (−)
Birefringenceδ = 0.208
PleochroismWeak, shades of yellow
2V angle80
Ultraviolet fluorescenceNone
SolubilityInsoluble
References[1][2][3][2]

Occurrence

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Carlfriesite is often found in cavities in hydrothermal gold-tellurium deposits. It is found associated with cerussite, chlorargyrite, argentian gold, cesbronite, calcite, dickite, baryte, bornite, galena, hessite and tlapallite.[5] It was first identified in the Bambollita (La Oriental), Moctezuma, Municipio de Moctezuma, Sonora, Mexico. It is also found in another nearby mine, namely the Moctezuma mine.

Synthesis

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Carlfriesite was found to be synthesizable by heating a mixture of CaO, Te(OH)6 and TeO2 to 150–240°C with water at the vapor pressure of the system. The resulting material was very fine-grained and colorless, consisting of aggregates of tiny carlfriesite plates. The material mostly consisted of carlfriesite, but also contained 10–15% paratellurite, as determined by X-ray diffraction.[6]

See also

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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. ^ Mineralienatlas
  3. ^ Barthelmy, Dave. "Carlfriesite Mineral Data". www.webmineral.com. Retrieved 2016-09-19.
  4. ^ "Carlfriesite: Carlfriesite mineral information and data". www.mindat.org. Retrieved 2016-09-19.
  5. ^ a b "Handbook of mineralogy" (PDF). Retrieved 2016-09-19.
  6. ^ a b Herta Effenberger; Josef Zemann; Helmut Mayer (1978). "Carlfriesite: crystal structure, revision of chemical formula, and synthesis" (PDF). American Mineralogist. 63. Retrieved 2016-09-19.