I'm doing my science homework now and i saw this so I'll just answer it. (9th), it is commonly known as rock salt

CRYSTAL STRUCTURE

What is the crystalline structure of halite, commonly known as rock salt? Recall that halite is composed of positively charged sodium ions bonded ionically to negatively charged chlorine ions. In the resulting pattern, each sodium ion is surrounded by 6 chlorine ions and each chlorine ion is surrounded y six sodium ions. his pattern is repeateted throughout the mineral. As a result of this arrangement of ions, halite typically occurs in crystals that have a cubic shape.

and here's just another thing...

NaCl Composition: Molecular Weight = 58.44 gm Sodium 39.34 % Na 53.03 % Na2O Chlorine 60.66 % Cl 60.66 % Cl - % Cl -13.69 % -O=Cl2 ______ ______ 100.00 % 100.00 % = TOTAL OXIDE Empirical Formula: NaCl Environment: Marine or continental evaporite deposits. IMA Status: Valid Species (Pre-IMA) Prehistoric Locality: World wide in sedimentary basins. Link to MinDat.org Location Data. Name Origin: From the Greek halos, meaning "salt" and lithos meaning "rock." Synonym: ICSD 18189 Murate of Sota PDF 5-628 Rock Salt Sodium Chloride

Source:

http://webmineral.com/data/Halite.shtml