(Kitco News) -CME Group is hiking silver margins again, with a late-Wednesday notice the fourth such announcement in the last two weeks.

CME Group, which operates the Comex division of the New York Mercantile Exchange, announced margin increases that will become effective at the end of business on Thursday, with yet another increase to go into effect after the close of business next Monday.

As of the end of business on Thursday, the “initial” margin to open new speculative positions in the main 5,000-ounce silver-futures contract will rise to $18,900 from $16,200, according to a notice released by the exchange. The “maintenance” margin for exiting speculative positions, as well as both initial and maintenance margins for hedger positions, will rise to $14,000 from $12,000.

Then as of the close of business on Monday, the initial speculative margin will rise further to $21,600. The speculative maintenance margin, as well as margins for hedgers, will increase to $16,000.

Margins are also rising for Comex MiNY silver futures and E-mini silver futures.

The notice from CME Group, which operates the Comex division of the New York Mercantile Exchange, said the change is a part of the “normal review of market volatility to ensure adequate collateral coverage.” The market has been volatile lately, with the most-active July futures contract surging sharply to $49.84 an ounce last week but subsequently pulling back as far as $38.94 and posting a decline of 7.5% on Wednesday.

The complete notice from CME Group can be seen at this link:

http://www.cmegroup.com/tools-information/lookups/advisories/clearing/files/Chadv11-159.pdf