Specimens from the south-west of the province are similar to those in the rest of the province, except that an alkali amphibole with anomalous optical properties occurs, both in lamproite blocks from the diatreme, and in an outcrop near a crocidolite quarry which includes both lamproite and country rock. The nature and extent of metasomatism may be significant in mapping and understanding the lamproite province. Both greisenisation and magnesium metasomatism have taken place.