The CME Group, which runs the the New York Mercantile Exchange, on Friday raised the margin on Comex gold futures by 21.48 percent and the margin on Comex silver margins by 15.63 percent.

CME increased the amount of money that parties trading gold and silver futures on the Comex division of the New York Mercantile Exchange must keep as good-faith deposits because of volatility.

We frequently adjust margins across all our products based on volatility, not prices, said CME spokesman Chris Grams.

Silver's price on the Comex this week fluctuated about 25 percent, while gold's price has fluctuated about 10 percent this week.