Halite is an evaporite mineral.  An evaporite mineral is one that forms when water evaporates and the minerals in the water crystallize into solid crystals.  Halite is composed of only two elements, sodium (Na) and chlorine (Cl).  It's chemical formula is NaCl, sodium chloride.  It belongs to a group of minerals that are chemically similar and are known as the halides.  


Halite is also known by its common name of Rock Salt.

Here is a list of halite's physical properties:
Color:  Colorless when pure; white, reddish, blue or purple.  The pink halite pictured here is from Searles Lake, California.  It gets its pink color from a reddish algae that grows in the lake water and is trapped in the halite when it crystallizes.
Hardness:  2.5
Specific Gravity:  2.1 to 2.6
Fracture:  Conchoidal (which means "shell-like")
Cleavage:  Perfect Cubic
Luster:  Glassy
Streak:  White

Halite is deposited in dried up lakes in very dry (arid) climates where the water evaporates and leaves behind the minerals that were dissolved in the water.  "Rock Salt" is found in very thick sedimentary beds deep underground.

---