I guess they are running out of sliver...

Wonder why the US mint has not sold a single ounce of silver so far in March? Here is a clue:

United States Mint Seeks Public Comment on Factors to be Considered in Research and Evaluation of Potential New Metallic Coinage Materials

WASHINGTON - The United States Mint today announced that it is requesting public comment from all interested persons on factors to be considered in conducting research for alternative metallic coinage materials for the production of all circulating coins.

Read more:
http://www.zerohedge.com/article/no-silver-no-problem-us-mint-would-know-if-you-will-accept-brass-steel-iron-or-tungsten-coin