Probably mis-identified and actually an alteration product of stibnite. The presence of bismutite appears very doubtful in view of Jensen's results.
Quality of samples:
not specified / average specimens
Confirmation
Validity:
Unconfirmed/Questioned
References
References:
http://www.smartminerals.com/cina2004/art_hunan.htm; Jensen, M. (2009): Mineralogy of the Yaogangxian Mine, Hunan Province, China. Mineral News 25(4), 1-11 & 14