Chenguodaite, approved by IMA-CNMMN (2004-042a), was discovered in the Bunan quartz vein-type gold deposit in the gold district
of East Shandong Peninsula. The mineral occurs in high grade Au-Ag-Cu ores, coexisting with galena, chalcopyrite, hessite,
electrum, unnamed Ag
6TeS
2 and Ag
16FeBiTe
3S
8, enclosed and replaced by native silver and acanthite. In the reflected light microscope, the mineral has light gray color,
indistinguishable anistropism and hardness around 2–3. The color indices of chenguodaite relative to ICE C illuminator are:
x=0.3027,
y=0.3076,
Y=25.78%,-λ
d=474 nm, Pe=3.68%, similar to those of canfieldite. The average chemical composition from 16 microprobe analyses is Ag
8.97Fe
1.00Te
1.99S
4.04, idealized to Ag
9FeTe
2S
4. The polycrystalline X-ray diffraction of chenguodaite by Gandolfi camera and synchrotron oscillation photography results
in 67 reflections with the 12 strongest being (relative intensity in bracket): 6.742(69), 6.416(39), 5.951(33), 3.265(100),
2.981(24), 2.649(22), 2.25(24), 2.188(71), 2.142(22), 2.123(31), 2.044(23), 1.949(33), which are indexed to a primitive orthorhombic
cell with
a=12.769 (2) Å,
b= 14.814(2) Å,
c= 16.233 (1) Å,
V= 3070.6 Å
3,
Z = 9, Dcal.=6.85 g/cm
3. The name is for the late Prof. Chen Guoda, a famous Chinese geologist and the founder of Diwa-Geodepression theory of tectonics.
Keywords chenguodaite - new mineral - tellurosulfide - synchrotron radiation - gold deposits - East Shandong
Supported by National Natural Science Foundation of China (Grant No. 40572027)