The crystal structures of gem-quality richterite and pargasite from Afghanistan, space group C2/m, Z = 2, have been refined to R1 indices of 2.47% and 3.22%, respectively, using MoKα X-radiation. Results from electron-microprobe analysis were used to calculate unit formulae and site populations were assigned using the refined site-scattering values and the observed mean bond-lengths. In pargasite, Al is strongly ordered at T(1) and Al is partly disordered over the M(2) and M(3) sites, whereas the M(1,2,3) sites are almost completely occupied by Mg in richterite. ANa is split between the A(2) and A(m) sites and K occurs at the A(m) site. The infrared spectra in the principal OH-stretching region were measured and the fine structure was fit to component bands that were assigned to short-range ion arrangements over the configuration symbol M(1)M(1)M(3)–O(3)–A–O(3):T(1)T(1), corresponding to the following local arrangements: MgMgMg–OH–Na–OH:SiSi; MgMgMg–OH–Na–F:SiSi; MgMgMg–OH–Na–F:SiAl; and MgMgMg–OH–□–OH:SiSi in richterite and MgMgMg–OH–Na–OH:SiAl; MgMgMg–OH–Na–F:SiAl; MgMgAl–OH–Na–OH:SiAl; and MgMgAl–OH–Na–F:SiAl in pargasite (□ = vacancy).