Reports & Proceedings — Mineralogical Society. 379 



REPORTS AND PROCEEDINGS. 



Mineralogical Society. 

 June 15. — Dr. A. E. H. Tutton, F.R.S., Past President, in the chair. 



F. P. Mennell : " Rare zinc-copper minerals from the Rhodesian 

 Broken Hill Mine, Northern Rhodesia."' Copper minerals, including 

 malachite, chessylite, copper-glance, and undetermined p>hosphates 

 are of rare occurrence in the lead-zinc ore of this locality. Still rarer 

 are the copper-zinc minerals aurichalcite and veszelyite ; the latter 

 forms minute, sky-blue, monoclinic crystals {a:h:c = "971 : 1 : '95), 

 and differs from the original mineral from Hungary in its colour 

 and in containing little or no arsenic. 



Professor R. Ohashi : " Note on the Plumbiferous Barytes from 

 Shibukuro, prefecture of Akita, Japan." This mineral, which is 

 deposited as a white to brownish-yellow crystalline crust in the 

 fissures and near the orifices of hot springs, is similar to the mineral 

 recently called " hokutolite " from Taiwan (= Formosa) ; it contains 

 4'69 to 17"78 per cent of PbO, and is radio-active. 



W. A. Richardson : "The Fibrous Gypsum of Nottinghamshire." 

 The relation to the nodular types of gypsum of the fibrous veins of 

 the mineral which are associated with every other type of gypsum 

 deposit in the district, and occur at levels v.^here there is no other 

 development of the mineral, was considered. Most of these veins 

 are regarded as having been formed shortly after the nodular 

 dcjoosits. The fibres grew upwards and downwards from a plane in 

 the marl, and were probably deposited by descending solutions, 

 being precipitated at planes of tension in a contracting medium. 

 The veins of fibrous calcium carbonate or " beef " described by 

 Dr. Lang show similar structure and field relations, and doubtless 

 originated under similar conditions. 



W. A. Richardson: "A new Model Rotating-stage Petrological 

 Microscope." This instrument is intended as a substitute for the 

 larger pre- War models, which at the present time could only be 

 manufactured at very high prices. It is provided with a mechanical 

 stage, interchangeable with a plane stage and a conventional sub- 

 stage, and provision is made for rapid change from parallel to 

 convergent polarized light. Owing to the reduction in size a rotation 

 of 270 degrees only can be provided for the rotating stage. 



W. Barlow : " Models illustrating the Atomic Arrangement in 

 Potassium Chloride, Ammonium Chloride, and Tartaric Acid." In 

 the case of the chlorides the suggested structure reconciles the X-ray 

 phenomena with the crystalline symmetry. The arrangement 

 proposed for tartaric acid agrees with the graphical formula of the 

 chemists, and the molecular groups have the symmetry and relative 

 dimensions of the crystals. 



