Kaňkite

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Kankite
General
Category Arsenate mineral
Formula
(repeating unit)
Fe3+AsO4·3.5(H2O)
Strunz classification 8.CE.60
Unit cell a= 18.803(15) b= 17.490(18) c= 7.633(5) z= 16
Identification
Formula mass 257.82 g
Color Yellowish–green
Crystal habit Tabular spearlike crystals in spherulites and botryoidal encrustations
Crystal system Monoclinic
Fracture Uneven
Mohs scale hardness 2 – 3
Luster Dull to vitreous
Streak Grayish yellow
Diaphaneity Translucent
Specific gravity 2.60 – 2.70
Optical properties Biaxial
Refractive index nα = 1.664 nγ = 1.680
References [1][2][3][4]

Kankite is a mineral with the chemical formula Fe3+AsO4·3.5(H2O). Kankite is named for the locality that yielded first specimens Kaňk, Czech Republic.[1] Kankite forms in old (1200–1400 year old) mine dumps.[2] It is yellowish-green on fresh exposure, with a paler greenish yellow on exposure to air.

Properties[edit]

Kankite is a monoclinic mineral, meaning it is a mineral system having 3 unequal axes of which one is at right angles with the other two. It has an uneven fracture and has a hardness of 2-3 (gypsum-calcite). It is translucent yellowish-green in color with a grayish yellow streak. It's luster is dull to vitreous. Kankite contains the elements arsenic, iron, hydrogen and oxygen.[3] It was approved by the IMA in 1976. It's habit is botryoidal, "grape-like" rounded forms (e.g. malachite). It forms encrustations, crust-like aggregates on matrix. The specific gravity of Kankite is 2.70.[2]

Occurrences[edit]

Kankite was first described in 1976 for an occurrence in the Kaňk, Kutná Hora, Bohemia, Czech Republic.[4] It is a rare secondary mineral in highly weathered mine dumps containing arsenopyrite (in the Czech Republic). It occurs in association with scorodite, pitticite, parascorodite, zykaite, arsenopyrite, vajdakite, native arsenic, pyrite, proustite, gypsum, “limonite” and quartz.[1]

It has also been reported from Munzig near Meissen; from Brand-Erbisdorf, Saxony; from Menzenschwand, Black Forest in Germany. It occurs at King’s Wood mine, Buckfastleigh, Devon, and from the South Terras mine, St. Stephen-in-Brannel, Cornwall in England. It has also been reported from the Suzukura mine north-northeast of Enzan, Yamanashi Prefecture, Japan.[1]

References[edit]

  1. ^ a b c d Handbook of Mineralogy
  2. ^ a b c Webmineral data
  3. ^ a b [1], Frost, Ray L. and Cejka, Jin and Keeffe, Eloise C. and Sejkora, Jiri (2009)Raman Spectroscopic study of the mixed anion sulphate-arsenate mineral pamnauiteJournal of Raman Spectroscopy, 40(11) pp. 1547-1550.
  4. ^ a b Mindat.org