Nitratine (also nitratite), also known as cubic niter (UK: nitre), soda niter or Chile saltpeter (UK: saltpetre), is a mineral, the naturally occurring form of sodium nitrate, NaNO₃. Chemically it is the Na-analogue of niter. Nitratine crystallizes in the trigonal system, but rarely occurs as well formed crystals. It is isostructural with calcite. It is quite soft and light with a Mohs hardness of 1.5 to 2 and a specific gravity of 2.24 to 2.29. Its refractive indices are nω=1.587 and nε=1.336.