Kampfite
Traskite (brown) and Kampfite (bluish), from Big Creek, Fresno County, California, United States of America
General
CategoryPhyllosilicate
Formula
(repeating unit)		Ba12(Si11Al5)O31(CO3)8Cl5
IMA symbolKpfb[1]
Strunz classification9.EG.20
Crystal systemMonoclinic
Crystal classDomatic (m)
(same H-M symbol)
Space groupCc
Unit cella = 31.2329, b = 5.2398
c = 9.0966 [Å]; β = 106.933°; Z = 1
Identification
ColorLight blue gray
Crystal habitIrregular grains or anhedral crystal inclusions
CleavageGood on {001}
FractureUneven
TenacityBrittle
Mohs scale hardness3
LusterVitreous
StreakWhite
DiaphaneityTranslucent
Specific gravity3.45
Optical propertiesUniaxial - (strongly pseudohexagonal)
Refractive indexnω = 1.642 nε = 1.594
Birefringenceδ = 0.048
References[2][3]

Kampfite is a rare barium silicate–carbonate–halide mineral with the chemical formula Ba12(Si11Al5)O31(CO3)8Cl5. Discovered in 1964 and described in 2001, it is named after Anthony R. Kampf. The mineral is known only from Fresno County, California.

Description

Kampfite is translucent and light blue-gray in color. Specimens occur as irregular masses up to 1 cm (0.39 in) in size.[4]

Composition and structure

When first described, the formula was identified as Ba6[(Si,Al)O2]8(CO3)2Cl2(Cl,H2O)2.[5] Subsequent work on analyzing the crystal structure led to a revised formula of Ba12(Si11Al5)O31(CO3)8Cl5. The structural H2O noted in the original description was not found in the later work.[6]

The structure consists of double layers of tetrahedra connected by barium-containing polyhedra. It is this layering which causes kampfite's one perfect cleavage.[7][8] Kampfite shares chemical and structural similarities with cymrite.[7] As of 2007, it is the only known barium silicate carbonate aside from fencooperite.[6]

Occurrence

Kampfite has been found in association with celsian, fresnoite, macdonaldite, pyrrhotite, titantaramellite, traskite, and witherite.[4] The mineral is known only from locations in Fresno County, California.[2][4] Kampfite is found in quartz-rich regions of sanbornite rocks[5] within gneiss which has undergone contact metamorphism associated with an adjacent granodiorite intrusive.[4]

History

The mineral discovered in 1964 by Robert Walstrom from the Esquire #1 claim of the Rush Creek deposit in eastern Fresno County.[9] It was described in 2001 in The Canadian Mineralogist.[5] The mineral was named kampfite in honor of Anthony Robert Kampf (1948–), curator of the Los Angeles County Museum of Natural History, for his crystallography work on new and rare minerals.[9]

Co-type specimens are held by the University of British Columbia and the Geological Survey of Canada.[10]

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. 1 2 Kampfite on Mindat.org
  3. ↑ Kampfite data on Webmin
  4. 1 2 3 4 Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C. (eds.). "Kampfite" (PDF). Handbook of Mineralogy. Chantilly, VA: Mineralogical Society of America.
  5. 1 2 3 Basciano et al. 2001, p. 1053.
  6. 1 2 Basciano & Groat 2007, p. 942.
  7. 1 2 Basciano & Groat 2007, p. 935.
  8. ↑ Basciano & Groat 2007, p. 940.
  9. 1 2 Basciano et al. 2001, p. 1054.
  10. ↑ Basciano et al. 2001, pp. 1054–1055.

Bibliography

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