Ammoniojarosite

ammoniojarosite

godovikovite

tschermigite

ammonioalunite

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Formula: (NH4)Fe3+3(SO4)2(OH)6
Anhydrous sulphate containing hydroxyl, alunite group, alunite supergroup
Crystal System: Trigonal
Specific gravity: 3.112 calculated
Hardness: 3½ to 4½
Colour: Light yellow; light yellow to nearly colourless in transmitted light
Solubility: Soluble in hot hydrochloric acid
Environments

Sedimentary environments
Coal-Seam fires

Localities

At the Dębieńsko Mine heap, Gmina Czerwionka-Leszczyny, Rybnik County, Silesian Voivodeship, Poland, ammonioalunite, ammoniojarosite and their solid-solution series were found on a burning coal dump. The minerals occur as yellow, fine-grained crusts and botryoidal masses in the outer part of a sulphate crust found about 1 m below the surface. The crust is composed mainly of godovikovite and tschermigite that formed by interaction of sour (containing significant amounts of hydrogen sulfide) fire gases or solutions and waste materials beneath the surface of the burning coal dump at temperatures of at least 80°C to 100°C. The crystals often reveal oscillatory zoning due to different aluminium and iron contents in thin bands. It is suggested that a complete solid solution between ammonioalunite and ammoniojarosite exists in nature (MM 74.4.731–745).

At the Zlatá Baňa deposit, Zlatá Baňa, Prešov District, Prešov Region, Slovakia, ammoniojarosite is associated with aluminite and natrojarosite (HOM).

At the type locality, the Kaibab fault, Kane County, Utah, USA, ammoniojarosite occurs in black lignitic shale containing pyrite. The ammoniojarosite forms small lumps and hard irregular flattened nodules up to 4 centimetres broad by 5 millimetres thick embedded in blackish-brown lignitic material. They frequently enclose small grains of the lignite and fibrous patches of tschermigite. Other associated minerals include epsomite and jarosite (AM 12. 424-426).

At the I90 roadcut, Buffalo, Johnson County, Wyoming, USA, ammoniojarosite has been found in black to brown shale of Eocene age (55.8 to 33.9 million years ago), about 15O m south of an area slightly altered by the burning of a coal bed. The ammoniojarosite occurred as an earthy, pale ocherous yellow powder coating on selenite crystals. The selenite crystals occur as vertical fracture-filling material within the shale (CM 20.91-95).

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