What mineral/or metal would oxidize to a orange powder in the motherlode gold country of California.?

This is in a 60 foot shaft with a wide vein of quartz containing visable galena and arsenopyrite,and one wall is a soft talc.What mineral/or metal would oxidize to a orange powder in the motherlode gold country of California.?
The only other possibilities are Realgar and Orpiment. These are associated with Arsenopyrite below and are Arsenic Sulfides. They are commonly orange and yellow and usually occur with Gold deposits more than the others mentioned.What mineral/or metal would oxidize to a orange powder in the motherlode gold country of California.?
Arsenopyrite, AsFeS, could oxidize to As2O3, FeO and SO2. FeO is hematite, commonly called rust, and could easily be the ';orange powder'; on the wall of the shaft. Pyrite FeS can be present and would oxidize to hematite. Any yellow powder could be limonite Fe(OH)3, which is commonly associated with hematite when pyrite oxidizes in the presence of water.
Are you heating in air?


Iron pyrite might go to a mixture of oxide and sulphate under some conditions.


In situ, you might be looking at ocher.