Formula: Fe(SO4).H2O
Hydrated sulphate, kieserite group, forms a complete solid solution with kieserite
Crystal System: Monoclinic
Specific gravity: 3.03 to 3.07 measured, 3.10 calculated
Hardness: 2½
Streak: White
Colour: Bluish, colourless, yellow, yellow-brown, light blue
Solubility: Dissolves in water very slowly
Common impurities: Cu,Co

Hydrothermal environments
Martian environments

Szomolnokite is an uncommon secondary mineral formed in pyrite-rich oxidised sulphide deposits, typically under highly acid and arid conditions. Associated minerals include rhomboclase, halotrichite, fibroferrite, römerite, copiapite, voltaite and pyrite (HOM).


At the Santa Elena Mine, Quebrada Alcaparrosa, Calingasta, Calingasta Department, San Juan Province, Argentina, szomolokite is associated with copiapite (Dana).

At the Alcaparrosa Mine, Cerritos Bayos, Calama, El Loa Province, Antofagasta, Chile, szomolokite is associated with römerite and rhomboclase (Dana).

At the El Indio deposit, Elqui Province, Coquimbo, Chile, the host rocks consist mainly of granite and breccia pipes. Hydrothermal activity produced two stages of alteration in which four types of mineralisation are recognised, based on the occurrence of economic concentrations of gold in rocks containing significant amounts of the following minerals:
(1) alunite, pyrite and enargite
(2) pyrite
(3) pyrite and szomolokite
(4) native gold
Main-stage gold mineralisation was followed by a sulphate stage represented by baryte and anglesite at lower elevations and baryte, anglesite and primary szomolokite, the first reported occurrence of this phase as a hydrothermal ore mineral, at higher elevations. Late-stage silver mineralisation enriched the upper parts of the deposit (EG 100.3.463-490).

At the type locality, Smolník, Gelnica District, Košice Region, Slovakia, szomolokite is associated with rhomboclase (Dana).

At the Rio Tinto Mines, Minas de Riotinto, Huelva, Andalusia, Spain, the soluble metal sulphate salts melanterite, rozenite, rhomboclase, szomolokite, copiapite, coquimbite, hexahydrite and halotrichite, together with gypsum, have been identified. Secondary iron sulphate minerals can form directly from evaporating, acid, sulphate-rich solutions as a result of pyrite oxidation. Melanterite and rozenite precipitates at Río Tinto are only found in association with very acidic drainage waters (pH <1.0), draining directly from pyritic waste piles. Copiapite precipitates abundantly by direct evaporation of the river water, or as part of a paragenetic sequence with the inclusion of minor halotrichite (MM 67.2.263-268).

At the Dolliver Memorial State Park, Iowa, USA, abundant sulphate efflorescences on sandstone consist of halotrichite, szomolokite and rozenite. Melanterite may occur in place of the lower hydrate, rozenite, during times of high humidity (CM 11.958).

At the North Mesa 5 Mine, Temple Mountain, San Rafael Mining District, Emery county, Utah, USA, szomolokite is associated with bobjonesite (Minrec 35.4.344).

On the surface of Mars, kieserite is a dominant sulphate species at lower latitudes. However, given the iron-rich composition of the Martian surface, it is very probable that its actual composition lies at an intermediate value along the solid-solution series between the kieserite and szomolokite end-members. The existence of a continuous kieseriteszomolokite solid-solution series on the Martian surface is proved (AM 104.1732-1749).

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