Kosher salt is not kosher, does
not come from the Dead Sea, is not necessarily blessed by a rabbi,
and may contain additives, although it is usually free from
iodine.
Kosher salt refers to any coarse-grain salt that is used to make
meat kosher. Kosher salt usually is mineral salt, which may mined
anywhere. A rabbi does not "bless" the salt to make it kosher
(although Morton's Coarse Kosher Salt in the past has claimed to
be packaged under Rabbinical supervision). As with any other salt,
some commercial Kosher salt, uses anti-caking additives to make it
free-flowing.