Ankaramite (pyroxene-phyric basalt)

This ankaramite is from the Palaeogene basaltic lava field at Barrington Tops, NSW. Ankaramites are pyroxene-phyric basaltic lavas. The dominant phenocryst phase in this sample are large titan-augite crystals along with minor olivine, both set in a fine-grained basaltic groundmass dominated by plagioclase. The titan-augite crystals are more obvious on the weathered surface and display the classic ~90° pyroxene cleavage. The Barrington Tops basalt field is dominated by tholeiitic and alkali basalt lavas associated with opening of the Tasman Sea and Southern Ocean. They have been dated at ~55 Ma.