Garnet crystals from diamondiferous high-pressure metamorphic rocks of the Kokchetav Massiv, Kazakhstan, were studied by electron microprobe and single crystal microscope-spectrometry in the UV/VIS and IR spectral ranges. The crystals are quaternary solid solutions Gross 48 Pyr 33 Alm 16 Spess 2 , (I.) from garnet-pyroxene-carbonate rock K7, and Gross 21 Pyr 24 Alm 49 Spess 5 , (II.) from garnet-biotite-gneiss, both with small TiO 2 -contents (0.3 wt%). Their yellow (I.) or deep-red colour (II.) is caused by the position of the UV absorption edge and a broad Fe 2+[8] Ti 4+[6] charge-transfer band centered at 21 500 cm −1 . For comparison, a high-pressure garnet Py26, Py 70 Alm 17 Uv 13 (III.), from Liaoning-50 kimberlite, NE China, was included in the IR and microprobe study. All crystals studied contained defect OH − -groups, corresponding to those in synthetic OH − -bearing pyropes, giving rise to a single, relatively sharp absorption band (Δv 1/2 ≃ 100 cm −1 ) in the range 3560 to 3610 cm −1 . The exact energy position depends on the type and site fractions of ions in the OH − -coordinating metal sites, A [8] and B [6] . This hydroxyl «water» seems to be not uniformly distributed in the garnet crystals and ranges from 0.02 to 0.25 wt% (wt% calculated from integral intensities using e i,Gross ). In addition to ν OH , the IR spectra show a broad band at 3400 cm −1 , characteristic of (H 2 O) n -clusters. There seems to be a constant ratio α i,OH− /(α i,OH− + α i,H2O ) for the various spots on the different crystals I, II, and III