Marcus, I don't know how much cobalt you are looking for. If you
are going to try alloying with gold you are probably talking about
small amounts. I buy 100 g quantities from Frey Scientific
(www.freyscientific.com) for redox reaction experiments. Other
suppliers are on the internet (check out Yahoo or Google). They
might be more reasonable on cost if you are looking for larger
amounts. World production of cobalt is about 17,000 tons per year.
It is listed as available in the form of foil, pieces, powder, rod
and wire. Care must be exercised in working with it. The toxic
intake is 500 mg. The lethal intake as the chloride (which I work
with) for the rat is 80 mg per kg. It tends to produce vomiting in
humans and is a suspected carcinogen. The metal is a lustrous,
silvery-blue color and is hard.
I hope this is of some use to you.
"Marlinespike Seamanship in Precious Metals"