Images
Formula: Mn3+O(OH)
Oxide containing hydroxyl, paramorph of groutite and
manganite
Crystal System: Trigonal
Specific gravity: 3.249 calculated
Streak: Brown
Colour: Lead-grey, brownish black
Luminescence: Not fluorescent under UV
Environments
Feitknechtite is a supergene mineral that typically forms
intergrowths with
hausmannite (MW). It is formed by
supergene oxidation and replacement of earlier
pyrochroite. Associated minerals include
pyrochroite
and hausmannite
(HOM).
Localities
At Långban, Filipstad, Värmland County, Sweden, feitknechtite occurs in altered
pyrochroite
(Dana).
At the Benallt Mine, Rhiw, Aberdaron, Gwynedd, Wales, UK, feitknechtite has been discovered as a component of
bladed
manganese ore,
as coarse brown bladed crystals consisting of an intimate mixture of
hausmannite and
feitknechtite, typical of what was once termed "hydrohausmannite". This ore is believed to have originally
consisted of
pyrochroite which altered on exposure to air
(MW).
At the type locality, the Franklin mine, Franklin, Franklin Mining District, Sussex County, New Jersey, USA, feitknechtite
occurs
as an alteration product of pyrochroite, and lining solution cavities in
a matrix of
calcite, sussexite and
zincite
(Dana). Associated minerals include pyrochroite and
hausmannite
(Mindat).
Back to Minerals