Yugawaralite in the Letaba Formation, northeastern KwaZulu-Natal, South Africa

The presence of the zeolite mineral yugawaralite (CaAl2Si6O16 . 4H(2)O) is reported in the Jurassic basaltic rocks of the Letaba Formation (Karoo Sequence) near Mkuze. Although many other members of the zeolite group have been reported from various localities in southern Africa, this is the first record of yugawaralite. The yugawaralite occurs in association with laumontite, wairakite, calcite, and quartz in an exposure of the basaltic rocks on the banks of the Mkuze River at 27 degrees 35.50S 32 degrees 00.30E, 5 km northwest of the town of Mkuze, northern KwaZulu-Natal. The presence of yugawaralite indicates that the basaltic rocks at Mkuze underwent a grade of alteration during the accumulation and post-eruptive development of the sequence different from that elsewhere in the region, as it does not fit into the previously published zones of regional diagenesis and metamorphism. It is suggested that the formation of yugawaralite at this site is related to a local dolerite dyke intruded at a very shallow depth.