Reports and Proceeding* — Miner a logical Society. 429 



IREJieOIRTS JUSTJD IPDROOIEIEIDinsrGrS. 



MlNERALOGICAL SOCIETY. 



Ane 13, 1911.— Professor W. J. Lewis, F.R.S., President, in 



the Chair. 



G. S. Blake: On Zirkelite from Ceylon. The results of five 

 analyses made on fragments grouped together according to their 

 specific gravity, which ranged from 5-2 to 4 - 4, showed remarkable 

 variation in the percentage composition, the densest containing about 

 20 per cent, thoria and little uranium, and the lightest 14 per cent. 

 U 3 8 and little thorium ; the precise formula is uncertain. A few 

 crystals, some simple and some twinned, were met with ; they 

 apparentlv belong to the hexagonal system (cr = 53° 22'), _the 

 observed forms being c (0001), tn (1010), r (1011), s (2021), a (1012), 

 e (2023), and r the plane of twinning; they were opaque in mass, 

 but translucent and isotropic in splinters. — Rev. Mark Fletcher : 

 Note on some Crystals of Artificial Gypsum. The crystals, which were 

 formed in the condensing plant of a distillery at Burton-on-Trent, were 

 twinned about 101, and the forms 100, 110, 230, 111 were observed. — 

 L. J. Spencer : The larger Diamonds of South Africa. Historical 

 notes relative to the ' Excelsior', 'Jubilee', and ' Imperial' diamonds 

 were given, together with a tabular statement of the weights of the 

 rough and cut stones in carats and grams, and the percentage yield of 

 the cut brilliants from the rough. — F. H. Butler : Brecciation in 

 Mineral Veins. In vein-breccias due to fracture in situ (crush-breccias) 

 replacement of country rock is a characteristic feature. Where the 

 coarse fragments in a brecciated fissure-vein indicate erosion, removal 

 of fine rock-debris may be inferred. Fragments that are angular and 

 uneroded and completely isolated by encrusting material often indicate 

 by shape and position their former existence as a single mass. The 

 quiet removal of such fragments into a vein-cavity after reunion, and 

 also the banding, with concomitant contortion of adjoining soft 

 country rock, by their cement-substance, may be ascribed to the 

 hydrostatic pressure and the solvent and mineralizing properties of 

 the waters which furnished that substance. The coarse constituents 

 of breccia may have been crushed in situ, or forced from fissure-walls 

 by earth-movements, or detached therefrom by aqueous pressure and 

 solution.— Arthur Russell : Prehnite from the Lizard District. Two 

 distinct types of crystals, tabular and prismatic, were recently found 

 by him on hornblende-schist at Pare Bean Cove, Mullion, Cornwall, 

 the former showing the forms 001, 302, 061, and the latter 100, 001, 

 110, 061, and the rare form 301. 



COEEBSPONDBNCE. 



DREIKANTER. 



Sir, — 1 am much indebted to Dr. Bather for pointing out, in your 

 June issue, that when I wrote ' a dreikanter ' I really meant 

 ' a Dreikante'. As a matter of fact I meant precisely what I wrote, 



