Hydrozincite from Narlarla, West Kimberley district, Western Australia

Extract

Hintze (1930) has pointed out the considerable variation in analyses of hydrozincite and the various formulae assigned to this mineral. Further data concerning this comparativeIy rare mineral are therefore desirable. Hydrozincite has been found at Narlarla, Western Australia, and this material is described below.

Narlarla is situated in the Napier Range, West Kimberley district (long. 124° 43′ E., lat. 17° 16′ S.), 75 miles due east from Derby, on the south side of the Barker River gorge (fig. 1). Several small silver-lead-zinc ore-deposits occur in the hills at Narlarla which are made up entirely of Devonian limestone. The occurrences have been described by Woodward (1907, p. 11), who, in his report, gives the results of assays of several specimens of the ore. These occurrences are Unique as they are the only known post pre-Cambrian primary ore-deposits in Western Australia. (Secondary gold deposits occur in the Donnybrook sandstone which is considered to be probably of Permian age (Forman, 1936).) The unique character of the Narlarla deposits has been noted by Simpson (1939, p. 218), who, however, offers no explanation as to their genesis. The absence of any post-Devonian igneous intrusives, other than the leucite-lamproite plugs (Wade and Prider, 1940) which are intrusive into the Permian rocks of the Fitzroy River area to the south of Narlarla, seems to indicate that these deposits are genetically related to the lamproite magma. The nearest known occurrence of the leucite-lamproites is at Mr. North, some 15 miles to the south (fig. 1), but there may be closer occurrences as the area has not been very closely examined, and the widespread distribution of the lamproite magma has been demonstrated (Wade and Prider, 1940).