table salt (halite crystals), magnified
A rock we eat!
If someone at the dinner table said, “Pass the rocks, please,” what
would you give that person?
Salt, of course!
The salt that people use to season food is a mineral called halite. Big
lumps of halite are found in the earth’s crust. The halite is dug out in
chunks and crushed up small enough to fit through the holes in a
saltshaker. Halite forms in square crystals. No matter how small it is
crushed, it nearly always breaks into the shape of a cube.
Sometimes, a hole is dug down to salt that is in the earth. Water is
forced down into the salt, then pumped back up with salt in it. The
water is then heated. When it dries up, crystals of pure salt are left.
Salt is removed from seawater in much the same way.
People need some salt to keep healthy, and many people think salt makes
food taste better. So salt has always been very important to people. In
ancient times, salt was so precious and hard to get that it was used as
money. The soldiers of ancient Rome were given salt as part of their
pay. This part of their pay was called the salarium. Our word
salary, which is another word for pay, comes from the Latin word
salarium. A man who was not a very good soldier was “not worth his
salt.” We still say this about people who don’t do a good job for the
money they are paid.
