Barquillite, Cu2(Cd, Fe)GeS4, a new mineral from the Barquilla deposit, Salamanca, Spain
Murciego, Ascensión; Pascua, Ma Inmaculada; Babkine, Jean; Dusausoy, Yves; Medenbach, Olaf; Bernhardt, Hans-Jürgen
European Journal of Mineralogy Volume 11 Number 1 (1999), p. 111 - 118
published: Feb 11, 1999
manuscript accepted: Oct 14, 1998
manuscript received: Aug 16, 1998
ArtNo. ESP147051101013, Price: 29.00 €
Abstract Barquillite, ideally Cu2(Cd, Fe)GeS4, is a new mineral species found in the Barquilla Sn-Ge-Cd-Cu-Fe vein-type deposit, Salamanca, Spain. This mineral occurs as plates and rosette-like aggregates of thin platy crystals, less than 50 μm in size. It is commonly in contact with tetrahedrite and chalcopyrite, less so with bornite, mawsonite, stannite and stannoidite. Barquillite is opaque, with a metallic luster. In reflected light, it has a grey colour with a violet tint, very weak pleochroism, very weak bireflectance, and is very weakly anisotropic. Reflectance spectra are given. The micro-indentation hardness ranges between 180 and 300 kg/mm2. The mean of thirty four analyses gives: Cu 30.67, Ag 0.26, Cd 20.38, Fe 2.20, Mn 0.43, Zn 0.09, Ge 14.99, Sn 0.17, Sb 0.09, Bi 0.16, Ga 0.05, S 29.42, a total of 98.91 wt.%, corresponding to: (Cu2.10Ag0.01)Σ2.11(Cd0.79Fe0.17Mn0.03Zn0.01)Σ1.00(Ge0.90Sn0.01)Σ0.91 S3.98(onthe basis of 8 atoms) or simply Cu2(Cd, Fe)GeS4. Based on the empirical formula and Z = 2, Dcaic = 4.53 g/cm3. The X-ray powder diffraction pattern obtained is analogous to that of briartite (JCPDS 25-282). The strongest X-ray powder diffraction lines are (d in Å(I)(hkl)): 3.10(100)( 112), 1.92(80)(220), 1.89(70)(204), 1.64(60)(312), 1.60(20)(303, 116) and 2.73(10)(200). The refinement of the lattice parameters leads to a = 5.45(4) Å and c = 10.6(1) Å, indexed by analogy to briartite. Barquillite is therefore a member of the stannite group, the Cd-dominant analogue of briartite. The name is given after the village of Barquilla, very near the type locality.