Carlfriesite

Carlfriesite
Carlfriesite from Moctezuma Mine, Moctezuma, Municipio de Moctezuma, Sonora, Mexico. Picture width: 2 mm.
General
Category	Tellurate minerals
Formula	CaTe^4+2Te^6+O8
IMA symbol	Clf[1]
Strunz classification	4.JK.25
Dana classification	34.5.3.1
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	C2/c
Unit cell	a = 12.576, b = 5.662 c = 9.994 [Å], Z = 4
Identification
Color	Bright yellow – buttery yellow
Crystal habit	Axe-head shaped crystals, botryoidal crusts or radial crystals.
Cleavage	Distinct
Tenacity	Brittle
Mohs scale hardness	3.5
Luster	Vitreous
Streak	Pale yellow
Diaphaneity	Transparent
Specific gravity	6.3 (measured) 5.7 (calculated)
Optical properties	Biaxial (−)
Birefringence	δ = 0.208
Pleochroism	Weak, shades of yellow
2V angle	80
Ultraviolet fluorescence	None
Solubility	Insoluble
References	^[1]^[2]^[3][2]

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.

Occurrence

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

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

• List of minerals
• List of minerals named after people

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. 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. "Handbook of mineralogy" (PDF). Retrieved 2016-09-19.
6. Herta Effenberger; Josef Zemann; Helmut Mayer (1978). "Carlfriesite: crystal structure, revision of chemical formula, and synthesis" (PDF). American Mineralogist. 63. Retrieved 2016-09-19.