• Reports & Proceedings — Mineralogical Society. 239 



IV. — Mineralogical Society. 

 March 18. — Sir William P. Beale, Bart., K.C., President, in the Chair. 



L. J. Spencer: "Curvature in Crystals." The curvature of 

 crystals is evidently of many different kinds, and due to as many 

 different causes. Numerous examples, figured in the literature and 

 illustrated by specimens in the British Museum collection of 

 minerals, are grouped under the headings : curved crystallites and 

 feathery microlites, capillary habit, aggregations of crystals, 

 interfacial oscillation, vicinal faces, bent crystals and plastic 

 deformation, twisted crystals, cylindrical (?) and spherical (?) 

 crystals (a supposition leading to a reductio ad absurdum). 



Lieut. A. B. Edge: "Siliceous Sinter from Lustleigh, Devon." 

 The district round Lustleigh, near Bovey Tracey, is mined on a 

 small scale for a very fine quality of micaceous hematite, which 

 occurs there in well-defined lodes traversing the granite. At the 

 Plumley Mine (now disused), on the walls of one of these lodes, is 

 found a peculiar banded material, somewhat resembling lithomarge 

 or halloysite, which on analysis proved to be a siliceous sinter or 

 opal, with an approximate percentage composition of silica 70, 

 water 21, hematite 6, alumina, soda and potash 3, and a low 

 specific gravity, 1-73. It is hard and compact, and shows a 

 beautifully banded structure, the layers being tinted to varying 

 degrees by limonite and finely divided flakes of micaceous hematite. 

 The general appearance of the material and the presence of delicately 

 overfolded ripples in the banding suggest that it was originally 

 deposited on the walls of the lode in the form of a jelly, and 

 solidified by loss of water. Such loss continues at a very slow rate 

 when specimens are kept in a dry atmosphere, and after some years 

 the surface becomes soft and powdery. The sinter is very fragile, 

 breaking conchoidally even when most carefully handled; this may 

 be caused by the shrinkage strains set up during solidification. 

 The source of this hydrated silica is rather doubtful ; it probably 

 formed part of the aqueous injection which deposited the hematite, 

 but may possibly have been leached from the granite during the 

 formation of the lode. 



A. P. Hallimond: "An Anorthic Metasilicate from Acid Steel 

 Furnace Slags." A description of the slags will be communicated 

 to the Iron and Steel Institute. The substance is a metasilicate of 

 iron, manganese, calcium, and magnesium, and appears as flat, 

 elongated crystals with_the following characters: Porms b (010), 

 »»(110), i/(110), f>(l"l2), J(10~l), «(310), constants a 99° 37', 

 /3 110° 57', 7 82° 3'; a : b : c = 1-156 : 1 : 0-497 ; perfect cleavages 

 parallel to m and M,mM = 95° 9J-' ; colour clear amber yellow, not 

 pleochroic; optical characters, 2V — 65 J°, negative, /3 = 1*701, 

 axial plane nearly normal to the cleavage zone, extinction on a 5°, 

 acute bisectrix nearly normal to a. 



Dr. C. T. Prior: "On the Meteorites Adare and Ensisheim." 

 The percentage amount of nickeliferous iron and the ratio of iron to 

 nickel in it were found to be respectively 18 and 13^ in the case of 

 Adare, and 3£ and 3J in the case of Ensisheim, which results support 



