Geology and Natural History. 323 



6. Structure- Planes of Corundum and some Massive Minerals 

 (simple rocks) from India and Australia ; by J. W. Judd (Min. 

 Mag., vol. xi, No. 50). — The author, as the result of his studies, 

 states that " corundum has at least three sets of structure-planes 

 but that none of these can be regarded as true cleavage. Two of 

 these structure-planes, those parallel to the baseOR(lll) and to 

 the prism oo P2(101) are normal solution-planes ; the third set of 

 structure-planes, those parallel to the unit rhombohedron R(100), 

 are gliding planes which when developed become secondary solu- 

 tion-planes." He also says that the partings observed " appear 



to be due to chemical alterations taking place along 



these structure-planes of the crystal." 



In the second portion of the paper an account is given of some 

 minerals which occur on so large a scale as to form veritable rock 

 masses. Some of these are occurrences of corundum at several 

 localities in India ; also rock masses made up of quite pure tourma- 

 line of a black color and in fibrous form. A rock composed entirely 

 of a green garnet is mentioned as occurring in dike form cutting 

 serpentine ; associated is another dike composed of nearly pure 

 picotite (chrome spinel). l. v. p. 



7. Remarkable phosphorescence in Wollastonite ; by W. F. 

 Hillebrand. (Communicated.) — In examining a fibrous mineral 

 recently received from New Hartford, Oneida County, N. Y., 

 which proved to be wollastonite, although of somewhat greater 

 hardness (about 5 '5) than the limit given in text-books, a most 

 beautiful greenish-yellow phosphorescence was observed. The 

 color is not very conspicuous by daylight, but in a dark room the 

 phenomenon is very strikingly shown when fragments are heated 

 below redness, or when the somewhat coarsely powdered mineral 

 is thrown into a hot, but not red-hot, crucible. 



Professor Penfield, to whom the specimen was sent, finds that 

 "the columnar and compact varieties from Bonaparte's Lake, 

 Lewis Co., N. Y., New Windsor, Orange Co., N. Y., and Bucks 

 Oo., Pa., show exactly the same phenomenon. Fragments of 

 crystals from Diana, Lewis Co., N. Y., and Dognaczka, Banat, 

 show only a slight phosphorescence, while a few of the crystallized 

 varieties that were tested do not show it at all. The com- 

 pact edelforsite of Hisinger, which Forchhammer (Danske Viden- 

 skab. Selskabs Forhandlingar, 1867, p. 64) by means of chemical 

 analysis has shown to be impure wollastonite, exhibits the phos- 

 phorescence beautifully." 



I may add that my own tests on material in the U. S. National 

 Museum show that different specimens from the same locality 

 may glow with very different intensities, as those from Natural 

 Bridge, Lewis Co., N. Y., for instance. Several Bucks Co., Pa., 

 specimens failed to phosphoresce, at least visibly, in daylight. 

 The beauty of the phenomenon and its novelty as regards this 

 species seem to merit publicity. 



Washington, U. S. Geological Survey. 



