Abstract: A borosilicate glass, containing 25 wt. % of simulated high-level radioactive waste has been reacted with water at 350°C and 500 bars for 14 and 48 days using large-volume ‘cold-seal’ high-pressure equipment. Under these conditions the glass crystallizes a suite of mineral phases including: albite, NaAlSi3O8; aegirine, NaFeSi2O6; riebeckite, Na2Fe2(Fe,Mg)3Si8O22(OH)2; zektzerite, LiNaZrSi6O15; barium-strontium molybdate, (Ba,Sr)MoO4; stillwellite, (Nd,Ce,La)BSiO5; willemite, Zn2SiO4; smectite; a lithium-sodium borosilicate hydrate; melilite (åkermanite), Ca2MgSi2O7. A description of the morphology of these phases is given, together with a number of chemical analyses. The implications of the incorporation of waste species in these mineral phases to the disposal of high-level radioactive waste is discussed.