Hello Ian,
as mentioned by Jose, most suasa also contains silver and it will be mostly silver sulphides contributing to any very dark patina.
Quote:
|
For these non-silver black oxidized pieces, I wonder if there might be some arsenic also in the mix. Some oxides of arsenic can be very black in appearance.
|
At least the 2 common oxides of arsenic are white.
It's the arsenate salts with metals like iron that are blackish (cp. warangan). Metallic arsenic in an alloy is a quite different kettle of fish though and unlikely to be more than a trace contaminant...
Quote:
|
I seem to recall that arsenic has some mystical properties in mainland SE Asia--certainly some of the Hmong who live in the Twin Cities used arsenic for medicinal purposes and I was told by members of that community that arsenic is a powerful substance in their culture.
|
Yes, arsenic compounds like realgar have been utilized in TCM (Traditional Chinese Medicine) for millennia and have a scientifically proven track record in modern medicine as well. However, there also are cancerogenic effects known...
Regards,
Kai