Z. Johan et al., BUCKHORNITE, PB2AUBITE2S3, FROM THE JILOV E GOLD DEPOSIT, CZECH-REPUBLIC, Comptes rendus de l'Academie des sciences. Serie 2, Mecanique, physique, chimie, sciences de l'univers, sciences de la terre, 318(9), 1994, pp. 1225-1231
Buckhornite, Pb2AuBiTe2S3, recently described as a new mineral (Franci
s et al., 1993), occurs in the Jilove gold deposit, Czech Republic. It
is associated with pyrite, nagyagite, tellurobismuthite, altaite, gal
ena, calaverite and native gold. Microprobe analyses gave the empirica
l formula Pb2.133Au1.033(Bi0.687Sb0.308)0.995Te2.048S2.952. Buckhornit
e is orthorhombic, P m m m or P 2 2 2; a = 9.374(4), b = 12.326(4), c
= 4.073(2) angstrom; V = 470.61 angstrom3, Z = 2; D(calc) = 8.347 g/cm
3. The electron diffraction study reveals a face-centred cubic sub-cel
l with a/3, b/6, c/2, whose dimensions correspond to [002], [022] and
[022BAR] of the PbS-PbTe solid solution unit-cell. Microprobe analyses
of associated angyagite gave Pb5.05gAu0.980(Sb0.861Bi0.255)1.116Te2,0
70S5.930. Consequently, the ideal formula can be written Pb5Au(Sb,Bi)T
e2S6. The association buckhornite + nagyagite makes it possible to est
imate the solubility limits of Sb and Bi respectively in the crystal s
tructures of these two mineral phases. These limits are close to 1/3 o
f Bi sites occupied by Sb in the buckhornite structure and to 1/4 of S
b sites occupied by Bi in the nagyagite structure.