Uvarovite garnet is an uncommon silicate matrix in chromitite seams in the Norite body of the Bushveld Igneous Complex, Transvaal, Union of South Africa. Separated uvarovite samples were analyzed chemically, and unit cell, specific gravity and refractive index values determined. Uvarovite, grossularite and andradite are the dominant “end members.” A linear relationship between chromic oxide content and physical properties is modified by titanium and iron. The deviations are discussed and estimated. The green color is tinged with brown where titanium and iron are high. The associated chromite grains have a chemical composition similar to that of nearby chromitite seams. Uvarovite-diopside layers between uvarovitc-bearing chromitite seams in the Eastern belt of the Norite are described. It is considered that the uvarovite was formed in pyroxenite and Chromitite where adequate chromium was available, by metamorphic metasomatic processes after the consolidation of the Norite body itself.
The pale green, fine-grained, ornamental rock known as South African Jade is found to be hydrogrossular that varies in composition over a restricted range near the grossularite end of the hydrogarnet series. Specific gravity and refractive index decrease with increase in combined water. The mineral replaces basic feldspar through zoisite, in anorthosite and feldspar-rich pyroxenite horizons near the Lower group of chromitite seams in the Western Belt of the Norite. The mineralogical changes are thought to be due to the addition of calcium in heated waters.