Petrography and mineral chemistry of two new ureilites, GRV 021512 and 022931, from the Grove Mountains, Antarctica, are reported in this paper. GRV 021512 exhibits a typical ureilite texture, and consists of 48.3% olivine, 9.4% pigeonite and 38.1% carbo- naceous interstitial material and/or reduction product. GRV 022931 has a cataclastic porphyritic texture, and consists of 19.1% olivine and 14.1% pigeonite embedded in 66.3% carbonaceous interstitial material and/or reduction product. The coarse-grained olivine and pigeonite in both meteorites have homogeneous cores, and they are FeO-rich within the range of the ferroan subgroup (subgroup I) of olivine-pigeonite ureilites. All olivine grains of the meteorites show reduction zones along boundaries and cracks. Abundant diamond coexists with graphite as graphite-rich patches and veins in the carbonaceous interstitial material. Petrogenesis of both meteorites and the origin of diamond are discussed. GRV 021512 exhibits a typical ureilite texture and consists of 48.3% olivine, 9.4% pigeonite and 38.1% carbo- GRV 022931 has a cataclastic porphyritic texture, and consists of 19.1% olivine and 14.1% pigeonite embedded in 66.3% carbonaceous interstitial material and / or reduction product. The coarse-grained olivine and pigeonite in both meteorites have homogeneous cores, and they are FeO-rich within the range of the ferroan subgroup (subgroup I) of olivine-pigeonite ureilites. All olivine grains of the meteorites show reduction zones along boundaries and cracks. Abundant diamond coexists with graphite as graphite-rich patches and veins in the carbonaceous interstitial material. Petrogenesis of both meteorites and the origin of diamond are discussed.