XXIV. ABSTRACT OF PROCEEDINGS. 



described. They occur in a coarse pegmatite vein. The remark- 

 able feature in them is the fact that instead of being modified 

 tetragonal pyramids with all their faces equally developed, they 

 have undergone a symmetrical distortion. In some cases this 

 distortion has produced pseudomonoclinic crystals, in other cases 

 pseudorhombic. Measurements of the interfacial angles proved, 

 however, that the crystals are really tetragonal. A pseudo- 

 rhombic modification of rutile is described in Dana's "System of 

 Mineralogy," (6th Edition) but no such modification of cassiterite 

 is described. The pseudomonoclinic distortion is believed to be 

 quite new. The amount of material available was insufficient for 

 chemical analysis, but blowpipe tests proved that it must be 

 almost pure tin oxide. Stereographic projections and figures of 

 the crystals are given. 



EXHIBITS. 



The following specimens were shewn by Mr. E. F. Pittman, 

 a.r.s.m. : — Four specimens, Ruby Hill, Bingara — (1) breccia con- 

 taining lumps of eclogite ; (2) eclogite consisting essentially of 

 garnet, diopside and bytownite felspar, this occurs as boulders in 

 the breccia ; (3) basalt containing eclogite, garnet etc., occurs as 

 a dyke cutting through the breccia-pipe ; (4) piece of basalt cut 

 to show an inclusion of garnet (pyrope) with a ring of kelyphite. 

 Quartzite traversed by veins of, and impregnated with precious 

 opal; White Cliffs Opal Fields. "Niggerheads," siliceous concre- 

 tions round a nucleus of wood ; White Cliffs Opal Field. Precious 

 opal, Ballina District ; this is found occupying cavities in basalt. 

 Green common opal, fifteen miles from Port Macquarie. Specimens 

 from the Peaks Mine, Burragorang — (1) quartz with native silver, 

 argentite and copper pyrites; (2) native silver with galena, mis- 

 pickel and copper pyrites ; the galena carries 170 ozs silver per 

 ton ; (3) fine-grained galena assaying from 600 to 800 ozs. per ton. 

 (4) pyrargyrite on quartz. Cosalite (sulphide of bismuth, lead 

 and silver), Duckmaloi Creek, Oberon District. Native bismuth, 

 Pheasant Creek, fifty miles east of Glen Innes, Gahnite (zinc 

 spinel) with galena, nine miles west Broken Hill. Rcepperite 



