Magnesium sulfate heptahydrate (Agriculture grade):

Appearance White small granular Main content 99.5% min MgSO4 48.59% min MgO 16.27% min Mg 9.81% min PH(5W/V%Sol) 5-8 Ferron(Fe) 0.002% max Chloride(CL) 0.002% Heavy metal (Pb) 0.001 %max Arsenic(As) 0.0002% max Insoluble 0.01%max Size (mm) 0.1-1 0.2-3 1-4