Tacharanite from Tasmania, Australia

THE mineral tacharanite has been recently re-examined by Cliff et al. (1975). They worked on material from the original locality, Portree, in Scotland (Sweet, I961) and from a few new European localities described between I97I and I974. None of the post-Sweet authors, however, refer to the second discovery of the mineral from Tasmania where it was identified by this writer in I961 and recorded in a number of publications (Sutherland, I965; Sutherland and Corbett, 1967; Sutherland and Hale 197o; Mines Department of Tasmania, 197o; Sutherland, 1973b). The first Tasmanian report was communicated to J. M. Sweet, who kindly arranged for the Department of Mineralogy, British Museum, to send the writer a small piece of the Portree material for study. As the Tasmanian find does not seem to be known in the later literature, some more detailed information on its occurrence is presented here for comparison with the European localities. Occurrence. The tacharanite is found at several localities in the Tertiary basaltic lavas of Tasmania and can be considered a relatively abundant mineral. It mostly occurs in hyaloclastite and hyaloclastite flow-foot breccias formed from flow or eruption of lava into water. These provide permeable and easily altered glassy rocks, forming suitable hosts for extensive deposition of secondary minerals. In the Marrawah-Redpa area and at Brittons Swamp in far NW. Tasmania the breccias formed through eruption into Miocene high seas, but near Gads Hill in the Mersey-Forth valleys, NW. Tasmania, and around Liawenee, Great Lake, Central Tasmania, the breccias represent mid-Tertiary eruptions into freshwater rivers and lakes. The lavas in these sequences are typically near-saturated alkali basalts and olivine tholeiites. There is one tacharanite occurrence (in amygdules) in a sub-aerial flow of olivine nephelinite, 3 km SW. of Scottsdale, NE. Tasmania. The writer is unaware of any tacharanite recorded from mainland Australia, probably because hyaloclastite breccias are much less common there and where they do occur they are usually much younger eruptives that have not been zeolitized. None of the European tacharanite is found in extensively seamed hyaloclastite breccias, but the writer has recently received an exchange specimen of glassy pillow lava with this secondary mineral from Naoki, Yaizu City, Shizuoka Prefecture, Japan. The material was sent by Dr. Tokiko Tiba, Department of Geology, National Science Museum, Tokyo, with the information that the tacharanite was identified by X-ray diffraction and that this first find from Japan is under study by Dr. A. Kato (Chief Curator of Minerals) and herself.