Abstract: Two olivines from the Spiegel river and Klaasvoogds melilite-basalts of the Cape Province are analysed. Optical properties for the olivines are given. These show excellent agreement with the chemical results. The olivines belong to the forsterite-fayalite series and do not contain significant amounts of Ca₂SiO₄. The presence of nepheline, leucite, analcime, apatite, and zircon in the Klaasvoogds melilite-basalt is described for the first time.