Dorallcharite, Tl (sub 0.8) K (sub 0.2) Fe (sub 3) (SO (sub 4) ) (sub 2) (OH) (sub 6) , a new member of the jarosite-alunite family

Dorallcharite, ideally TlFe (super 3+) (sub 3) (SO (sub 4) ) (sub 2) (OH) (sub 6) , is a Tl-Fe member of the alunite-jarosite family. It occurs in the oxidation zone of the As-Tl orebody at Allchar, Republic of Macedonia, where it is associated with an amorphous Fe- Mn sulphate-arsenate free of Tl. EPMA results show that K substitutes 8.3-29.5% (mean 18.6%) of the Tl atoms. A complete solid-solution series is assumed to exist between dorallcharite and jarosite. Indexed XRD powder dataare tabulated; strongest lines 3.112(100), 5.974(87), 3.666(34), 1.991(29), 1.833(23) Angstrom ; a 7.3301, c 17.6631 Angstrom ; space group R3m; Z = 3; D (sub calc.) 3.85 g/cm (super 3) . The mineral has a golden yellow colour (the name is for the colour [dore in French] and the locality) and forms earthy and fine-grained aggregates of rhombohedral crystals < 10 mu m in diameter with a distinct 0001 cleavage; it has epsilon 1.768, omega 1.822, and is colourless to brownish yellow with no pleochroism.