382 Rejjorts c& Proceedings — Mineralogical Society. 



MiNERALOGICAL SOCIETY. 



^Ith June. — Dr. A. Hutchinson, President, in the chair. 



A. Beammall and H. F. Harwood : The Dartmoor Granite ; its 

 Accessory Minerals and Petrology. 



Minerals of general occurrence — tourmaline, ilmenite, magnetite, 

 apatite, monazite, garnet, zircon — (I) in water clear, small crystals, 

 (2) in tawny, zoned, larger, and more abundant crystals, pyrites 

 and pyrrhotite. More restricted : fluor (colourless, blue, and 

 purple), topaz, cassiterite, andalusite, sphene, anatase, barytes. 

 Biotite is abundant : muscovite is scanty. Streams have yielded, 

 in addition, rutile, brookite, and blue-green anatase. Analyses are 

 given of granite types (bulk), biotite, porphyritic felspars (baryta- 

 bearing), and some accessory minerals. The Tor area (Haytor- 

 Widecombe) is mapped, to show that the granite occurs as 

 successive shoots or flows, differing appreciably in chemical 

 composition. Texture becomes coarser, porphyritic felspars become 

 more abundant and richer in plagioclase content, percentage of 

 biotite and accessoiies increases with vertical descent in a flow. 

 The relationship of topography to pseudo-bedding, jointing, 

 veining, and probable faulting is discussed. 



W. F. P. McLiNTOCK and F. E. Ennos : On the structure and 

 composition of the Strathmore meteorite. 



A description is given of the microscopical characters as seen in 

 thin sections of this meteorite, stones of which fell in Perthshire 

 and Forfarshire on 3rd December, 1917. The structure is that of 

 the intermediate chondrite group (C i). An apatite-like mineral is 

 present. Detailed chemical analyses of the magnetic and non- 

 magnetic portions agree closely with the Baroti group. 



Henry F. Collins : On some crystallized sulphates from the 

 province of Huelva, Spain. 



Analyses aie given of pisanite, chalcanthite, coquimbite, copiapite, 

 voltaite, roemerite, etc., from various pyrites mines. Experiments 

 were made to determine the range of miscibility of iron sulphate 

 and copper sulphate in mixed crystals of pisanite (E'SO^.THgO) 

 and chalcanthite (R"S04.5H20). 



Harold Hilton : The graphical construction of the constants 

 of a shear. 



A graphical construction, based on the gnomonic projection, is 

 given for obtaining the two circular planes of a shear, when the 

 initial and final positions of two crystal-poles or edges are known. 



Harold Hilton : A note on crystallographic notation. 



A notation is suggested for the thirty-two crystal-classes and the 

 230 groups of movements, which is easy to write and print, and is 

 based on the fundamental principles of structure-theory. 



A. F. Hallimond (with chemical analysis by E. G. Radley) : 

 On glauconite from the Greensand near Lewes, Sussex : the 

 constitution of glauconite. 



