Batoniite

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Formula: Al₈(SO₄)₅(OH)₁₄(H₂O)₁₈.5H₂O
Sulphate
Crystal System: Triclinic
Specific gravity: 1.949 calculated for the ideal formula
Streak: White
Colour: White to colourless
Luminescence: No fluorescence under UV
Solubility: Slowly soluble in water
Environments

Sedimentary environments
Hydrothermal environments

Batoniite is a new mineral, approved in 2023 and to date (January 2024) reported only from the type locality. It bears a most unlikely [Al₈(OH)₁₄(H₂O)₁₈]¹⁰⁺ cluster.

Localities

At the type locality, Le Cetine di Cotorniano Mine, Chiusdino, Siena Province, Tuscany, Italy, the mine exploited an antimony ore deposit whose origin is related to widespread hydrothermal activity. The mineralisation consists of jasperoid and vuggy silica masses replacing host rocks at the contact with the overlying argillic formations. Ore minerals are mainly represented by stibnite, whereas iron sulphides, pyrite and marcasite, are accessory phases. As well as batoniite, the Cetine di Cotorniano Mine is the type locality for four other mineral species, brizziite, cetineite, onoratoite and rosenbergite. Moreover, the mine is also known for the occurrence of some rare halides, elpasolite and hydrokenoralstonite, as well as onoratoite and rosenbergite.
In the type material, batoniite occurs as hemispherical aggregates, up to 1 mm in diameter, formed by tabular crystals, associated with gypsum and a poorly crystalline resinous orange-brownish, still undetermined aluminium-iron sulphate. The specimen was collected in the Garibaldi Tunnel, the lowest mining level of the Cetine mine; these mining works were excavated within Paleozoic (541 to 252 million years ago) metasediments. Aluminum sulphates are common secondary minerals usually related to the action of SO₄-rich solutions on aluminium-bearing rocks. This condition can be observed in acid mine drainage systems as well as in fumarolic and hydrothermal environments. The crystallization of batoniite is probably related to the action of H₂SO₄, produced through the oxidation of pyrite, on Al-bearing rocks in the Garibaldi Tunnel. In the same occurrence, other Al-bearing sulphates are known, such as jurbanite and alunogen (EJM 35.5.703-714)

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