Nitratine (also
nitratite), also known as
cubic niter (UK:
nitre),
soda niter or
Chile saltpeter (UK:
Chile saltpetre), is a mineral, the naturally occurring form of
sodium nitrate, NaNO
3. Chemically it is the sodium analogue of
saltpeter. 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.