Hallo,
Gibt es schon eine genauere Beschreibung des Minerales ?
klar
Mills, S. J., Grey, I. E., Mumme, W. G., Miyawaki, R., Matsubara, S., Bordet, P., Birch, W. D. & Raudsepp, M. (2008) Kolitschite, a new arsenate mineral from Broken Hill, New South Wales, Australia. Australian Journal of Mineralogy, 14(2), 15–19.Abstract
Kolitschite, ideally Pb[Zn0.5,□0.5]Fe3(AsO4)2(OH)6, where □ = vacancy, (IMA 2008–063), is a newly defined mineral from the Kintore opencut, Broken Hill, New South Wales, Australia. Kolitschite occurs as steeply pseudorhombohedral crystals to 0.2 mm associated with mimetite, segnitite, carminite, bayldonite and cryptomelane. The main forms observed are {110} (prism) and {001} (pinacoid). Kolitschite crystals are yellowish green with a light yellow streak and are transparent to translucent with an adamantine lustre. Mohs hardness is 4, no cleavage was observed and all crystals are twinned. Kolitschite is monoclinic, C2/c, with a = 25.8898(6), b = 14.8753(2), c = 12.1700(2) Å, β = 110.681(1)°, V = 4384.9(2) Å3 and Z = 16. Kolitschite crystals are biaxial (+), with estimated indices of refraction n = 2.0. 2V is ≤ 10°. Orientation: Y = b, with straight extinction and very weak pleochroism: X = green to olive green, Y = green to olive green, Z = yellowish green to apple green. Absorption: X ≈ Y > Z. The simplified formula (on the basis of [As+P+S] = 2 and OH- = 6) is: Pb[Zn0.25,□0.75]Fe3[(HAsO4)0.50(AsO4)1.50](OH)6, which requires Zn 2.12, Pb 26.86, Fe 21.72, As 19.42, O 29.03, H 0.85, total 100.00. A solid-solution series extends towards the end-member composition of Pb[Zn0.5,□0.5]Fe3H0.5(AsO4)2(OH)6, with the single-crystal structure giving a charge-balanced empirical formula of Pb[Zn0.439,□0.561]Fe3H0.061(AsO4)2(OH)6. The strongest five powder-diffraction lines [d in Å, (I/Io), (hkl)] are: 3.114, (100), (621, 62-3, 04-2); 6.034, (45), (400, 22-1); 2.280, (37), (404, 22-5); 3.719, (31), (62-1, 040); 2.844, (25), (004). Kolitschite is related to members of the alunite supergroup, in particular segnitite. The mineral is named for Dr Uwe Kolitsch (b. 1966), for his contribution to mineralogy.
Gruß
Berthold