China Gold Panda, brown/red spots

I've seen some China Gold Panda bullion coins with brown/red spots on
them.
Is this due to poor quality of the Chinese coin manufacture?
Didn't think this would happen on pure .999 gold coins, never saw on
any other gold bullion coins.
I have seen and heard about it on 90% gold coins like Mexico Pesos.
Anyone else got experience why the China .999 gold coins would develop
spots?

This is probably due to a reddish tarnish caused by silver/gold
sulphide. It is relatively common even with 999 gold. The silver may be
present in very small quanities in the bulk of the gold or more likely
is a surface contamination. This surface contamination if often picked
up where gold and silver items are produced on the same mills, presses
etc.

Regards,

Robert

jondo220 wrote:
I've seen some China Gold Panda bullion coins with brown/red spots on
them.
Is this due to poor quality of the Chinese coin manufacture?
Didn't think this would happen on pure .999 gold coins, never saw on
any other gold bullion coins.
I have seen and heard about it on 90% gold coins like Mexico Pesos.
Anyone else got experience why the China .999 gold coins would develop
spots?

"jondo220" wrote in news:1134364659.253153.275300
@g47g2000cwa.googlegroups.com:

I've seen some China Gold Panda bullion coins with brown/red spots on
them.
Is this due to poor quality of the Chinese coin manufacture?
Didn't think this would happen on pure .999 gold coins, never saw on
any other gold bullion coins.
I have seen and heard about it on 90% gold coins like Mexico Pesos.
Anyone else got experience why the China .999 gold coins would develop
spots?


I have an 1999 Australian 1ox kangaroo which also exhibits a small red
spot. so its not unique to China.

wrote:
This is probably due to a reddish tarnish caused by silver/gold
sulphide. It is relatively common even with 999 gold. The silver may be
present in very small quanities in the bulk of the gold or more likely
is a surface contamination. This surface contamination if often picked
up where gold and silver items are produced on the same mills, presses
etc.

Gold sulfide? Would that be more likely pre or post production?