
U.K.-based clearing house LCH.Clearnet Group Ltd. said Tuesday that it will accept gold as collateral for margin cover purposes starting Aug. 28.
The clearing house said the option would be available for members clearing over-the-counter precious metals forward contracts or precious metals contracts on the Hong Kong Mercantile Exchange.
The clearing house limited the amount of gold that could be used as collateral to no more than 40% of the total margin cover requirement for a member across all products and at a maximum of $200 million, or roughly 130,000 troy ounces, per member group.
http://articles.marketwatch.com/2012-08-21/markets/33296795_1_precious-metals-total-margin-contracts

Tradition.