In the latest snapshot this block is removed because of Quarts Block ID.
It is as far as I know a glitched or accidental block however is widely used amongst the community as a use full decorative block.

It has been removed as the block ID is now used for quarts block and, seeing as though the only way to obtain this block with the /give command, will no longer be in the game at all even if already placed.

It would be great to have it re added as its a great alternative to building stone structure's.

Please consider. Thanks.
-J.V