The CME Span Margin Credit for a Gold (GC) versus Silver (SI) spread is 75% and the exchange listed ratio is 1:1 for the inter market spread.
http://www.cmegroup.com/trading/met...sector=METALS&clearingCode=CX-SI&pageNumber=1
http://www.cmegroup.com/trading/met...sector=METALS&clearingCode=CX-SI&pageNumber=1
