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Formula: Fe3+(SO4)(OH).2H2O
Hydrated sulphate containing hydroxyl, monoclinic paramorph of
parabutlerite, which is orthorhombic. Butlerite is sometimes epitaxial
on parabutlerite.
Crystal System: Monoclinic
Specific gravity: 2.548 measured, 2.53 calculated
Hardness: 2½
Streak: Pale yellow
Colour: Dark orange, light yellow-orange in transmitted light.
Environments
Hydrothermal environments
Mine fires
Butlerite is rarely formed from the oxidation of pyritic ore and it may be
formed under fumarolic conditions in mine fires. Associated minerals include
parabutlerite, copiapite,
fibroferrite and other iron sulfates
(HOM).
Localities
At the Santa Elena Mine, Quebrada Alcaparrosa, Calingasta, Calingasta Department, San Juan Province, Argentina, butlerite
occurs as oriented intergrowths with parabutlerite
(AM 27.144).
The type locality, the United Verde Mine, Black Hills, Yavapai county, Arizona, USA, hosts six type minerals that formed as the
result of a mine fire that started in 1894 and burned for decades (R&M 87.1.10 ). Butlerite was formed by the oxidation
of pyrite in the fire with reactions with water, steam and carbon dioxide used for fire
fighting. It is associated with copiapite
(Mindat, Dana).
At the Dexter group, Calf Mesa, San Rafael Mining District, Emery county, Utah, USA, the
paramorphs butlerite and
parabutlerite occur as encrustations of small crystals with
copiapite or melanterite
(AM 40.478).
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