THE commonest associate of galena is blende ; and almost all lead ores have to be " dressed " or concentrated in order to separate as much as possible of this objectionable material, as well as of the gangue. The usual products of dressing-works handling argentiferous zinc-lead sulphides are the following :.1. Concentrates of various degrees of fineness ranging from 6-mesh first jig hutchwork down to too-mesh " headings " from the slime-tables, and in composition from 8o per cent. lead down to perhaps 55 or 6o per cent., which is a common figure at Broken Hill.2. Middlings of varying composition ranging according to the adaptability of the ore to concentration, from an almost clean blende down to the intimate mixture of blende, galena, and heavy gangue minerals, with perhaps 3o per cent. Zinc and 20 to 30 per cent. lead, which forms such a troublesome product at Broken Hill.3. Tailings ranging from almost clean gangue-stuff up to a material with 10 per cent. zinc, and perhaps 6 per cent lead, which, under some conditions, will not pay for further grinding and treatment.4. Slimes of very variable composition, carrying from 15 to 25 per cent. zinc, and from 25 to 35 per cent. lead, the remainder being gangue.