Kankite | |
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![]() Kaňkite found in the Czech Republic | |
General | |
Category | Arsenate mineral |
Formula (repeating unit) | Fe3+AsO4·3.5(H2O) |
IMA symbol | Kňk [1] |
Strunz classification | 8.CE.60 |
Crystal system |
Monoclinic Unknown space group |
Unit cell | a = 18.803(15), b = 17.490(18) c = 7.633(5) [Å]; β = 92.72°; z = 16 |
Identification | |
Formula mass | 257.82 g/mol |
Color | Yellowish–green |
Crystal habit | Tabular spearlike crystals in spherulites and botryoidal encrustations |
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 | [2] [3] [4] [5] |
Kankite is a mineral with the chemical formula Fe3+ As O4·3.5( H2O). Kankite is named for the locality that yielded first specimens Kaňk, Czech Republic. [2] Kankite forms in old (1200- to 1400-year-old) mine dumps. [3] It is yellowish-green on fresh exposure, with a paler greenish yellow on exposure to air.
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. Its luster is dull to vitreous. Kankite contains the elements arsenic, iron, hydrogen and oxygen. [4] It was approved by the IMA in 1976. Its 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. [3]
Kankite was first described in 1976 for an occurrence in the Kaňk, Kutná Hora, Bohemia, Czech Republic. [5] 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. [2]
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. [2]