"Matt Shepherd" wrote in message
m...
A friend of mine just passed on a translucent blue-tinged crystal he
calls a "salt rock," telling me if I put it in my puffer tank it will
slowly release the appropriate amount of salt in the water for them
over time.

It doesn't seem particularly water-soluble, nor does it taste like
salt.

Anyone here know of such a thing?


Yep there is, there are many deposits of salt under ground. Gulf coast,
Paradox basin in NM, Wyoming overthrust, Montana, Permian basin and the Salt
Range of Pakistan to name just a few of the places I've had personal contact
with rock salt. Pure NaCl tends to be clear, a bit of KCl mixed will give
you pink.

DONOT put it in the tank, it will rapidly disolve and produce a hypersaline
tank killing most everything. It SEEMs less soluble because it is not
ground up, but it will dissolve in a short time .

http://www.saltinstitute.org/14.html

http://www.greatsouth.net/p-M439.html

Bob
gray bearded geologist of some 35 year prof. experience.