Amarantite
Amarantit is a rarely occurring mineral from the mineral class of " sulfates ( and Related ) ". It crystallizes in the triclinic crystal system with the chemical composition Fe23 [O | (SO4 ) 2] • (3 4) H2O and usually develops only small, prismatic crystals to about 2 cm or acicular, radiating aggregates of amaranth red to brownish- red or orange-red color in lemon yellow stroke color.
Special Features
Amarantit is readily soluble in water and weathered ocher -like after some time.
Etymology and history
Amarantit was first discovered in 1888, named in the La Compañia mine at Caracoles in the province of Tocopilla, Antofagasta Región de Chile and described by Friedrich August Frenzel, who αμάραντος the mineral because of its characteristic color from the Greek word for amaranth.
Classification
In the now outdated but still in use 8th edition of the mineral classification by Strunz the Amarantit to the mineral class of " sulfates, selenates, tellurates, chromates, molybdates, tungstates " and then to the Department of " water -containing sulfates with foreign anions " belonged, where he with Butlerit, Fibroferrit, Hohmannit, Metahohmannit, Parabutlerit and Xitieshanit formed a distinct group.
The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the Amarantit also in the class of " sulfates ( selenates, tellurates, chromates, molybdates and tungstates ) " and then in the Department of " Sulfate ( selenates, etc.) with additional anions, with H2O" one. This division, however, is further divided according to the size of the involved cations and the crystal structure, so that the mineral in accordance with the subdivision " with medium-sized cations; isolated octahedra and limited units "can be found, where it forms the unnamed group 7.DB.30 together with Hohmannit and Metahohmannit.
The mostly commonly used in English-speaking classification of minerals according to Dana assigns the Amarantit in the class of " sulfates, chromates, molybdates ," and there in the department of " water -containing sulfates with hydroxyl or halogen". Here he is the only member of the unnamed group 09.31.03 within the sub-division of " water -containing sulfates with hydroxyl or halogen with (A B2 ) ( XO4 ) Zq × x (H2O) ".
Education and Locations
Amarantit is a secondary mineral that forms particularly under arid climatic conditions. Accompanying minerals include Hohmannit, Fibroferrit, Chalkanthit, Copiapite, Coquimbit and Sideronatrite.
Worldwide, Amarantit so far (as of 2010) are detected in 20 localities. In Chile, he stepped up to his type locality La Compañia mine still at several sites in the Región de Antofagasta and in Tierra Amarilla ( Atacama region ) and in the Pampa del Tamarugal evident.
Other localities include the Santa Elena Mine in La Alcaparrosa (San Juan ) in Argentina; the Mutooroo mine at Pine Creek ( Northern Territory ) in Australia; Yazd, Iran; the Calamita mine Capolivieri in Italy; Otta in Norway; Dubník ( Červenica ) in Slovakia as well as in Blythe (California ) in San Juan County (New Mexico) and in the Broken Hill Mine (South Dakota) in the United States.
Morphology
Usually occurs Amarantit in the form of wide-ranging, radialstrahliger or feinnadeliger to matted aggregates. Rarely well formed crystals are often elongated prismatic of approximately square cross-section and along the c-axis, wherein the surfaces in the direction of the dominant A- and B-axis. Tabular formed also in the direction of a-axis crystal and perpendicular to the c- striped axis crystal faces are known. In total, more than 60 different crystal forms have been documented so far.
Crystal structure
Amarantit crystallized in the triclinic space group with lattice parameters a = 8.98 Å; b = 11.68 Å; c = 6.70 Å; α = 95.6 °; β = 90.4 ° and γ = 97.2 ° and two formula units per unit cell.