Fraipontite
Pockets of minute pearly white fraipontite crystals with green smithsonite from Laurium, Greece (size: 1.4 x 1.0 x 0.9 cm)
General
CategoryPhyllosilicate
Formula
(repeating unit)		(Zn,Al)3(Si,Al)2O5(OH)4
IMA symbolFpt[1]
Strunz classification9.ED.15
Crystal systemMonoclinic
Crystal classDomatic (m)
(same H-M symbol)
Space groupCm
Unit cella = 5.34, b = 9.21
c = 14.12 [Å]; β = 93.2°; Z = 2
Identification
ColorBlueish, yellow white light green
Crystal habitFibrous to porcelaneous massive
Mohs scale hardness3.5 – 4
LusterSilky
StreakWhite to pale green
DiaphaneityOpaque to translucent
Specific gravity3.08 – 3.10
Optical propertiesBiaxial (-)
Refractive indexnα = 1.620 nβ = 1.624 nγ = 1.624
Birefringenceδ = 0.004
2V angleMeasured: 15° to 20°
References[2][3][4]

Fraipontite is a zinc aluminium silicate mineral with a formula of (Zn,Al)3(Si,Al)2O5(OH)4.[2][3]

It is a member of the kaolinite-serpentine mineral group and occurs as an oxidation product of zinc deposits. It occurs with smithsonite, gebhardite, willemite, cerussite and sauconite.[2]

It was first described in 1927 for an occurrence in Vieille Montagne, Verviers, Liège Province, Belgium.[3] It was named for Julien Jean Joseph Fraipont (1857–1910), and Charles de Fraipont, geologists of Liege, Belgium.[4] In addition to the type locality in Belgium, it has been reported from Tsumeb, Namibia; Laurium, Greece; Swaledale, North Yorkshire, England; the Silver Bill mine, Cochise County, Arizona, the Blanchard Mine, Socorro County, New Mexico and the Mohawk mine, San Bernardino County, California in the US; and from the Ojuela mine, Mapimi, Durango, Mexico.[2]

A synonym of the fraipontite is the zinalsite, which was reported in 1956 for an occurrence in Kazakhstan.[5][6]

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 3 4 Handbook of Mineralogy
  3. 1 2 3 Mindat.org
  4. 1 2 Webmineral data for fraipontite
  5. ↑ Zinalsite on Webmineral
  6. ↑ Zinalsite on Mindat

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