70 Scientific Intelligence. 



and breaks with a perfectly conchoidal fracture. If, however, 

 gliding planes and lamellar twinning be developed in corundum 

 (like those so easily produced in the same way in calcite), parallel 

 to the fundamental rhombohedron of the crystals, then these 

 gliding planes become " solution planes," along which chemical 

 action takes place most readily. Along the primary or secondary 

 solution planes, hydration of the aluminium oxide takes place, 

 and diaspore is formed, as shown by Lawrence Smith and Genth, 

 and this unstable mineral enters into combination with silica and 

 other oxides present to give rise to the numerous pseudomorphs 

 of corundum, which are so well known to mineralogists. 



There are certain crystals of corundum and spinel from Burma 

 which present illustrations of corrosion of a very remarkable and 

 interesting character. Commencing with the formation of natu- 

 rally etched figures (" Verwitterungsfiguren "), the work of cor- 

 rosion goes on till the whole crystal is broken up into an aggre- 

 gate of simple forms — these being, in the case of the spinel, the 

 octahedron, and, in the case of the corundum, a combination of 

 the rhombohedron, basal plane, and prism. 



It is interesting to note that the quartz, feldspars, and other 

 minerals associated with the rubies and spinels of Burma, exhibit 

 phenomena of external etching and internal chemical change 

 similar to those we have been describing in the case of the gems. 

 The study of the whole of the phenomena throws much new light 

 on the remarkable changes which take place, at great depth in 

 the earth's crust, in minerals which, at the surface, appear to be 

 of a very stable character." — Proc. Roy. Soc, No. 345. 



9. Brief notices of some recently described Minerals. — Aschae- 

 ite is a hydrous magnesium borate found in white lumps asso- 

 ciated with boracite in the rock salt of Schmidtmannshall near 

 Aschersleben. Specific gravity 1 '85-1 -95. The mean of three 

 analyses gave : 



B 2 3 49-2 MgO 42-8 H 2 8-0 = 100. 

 Described by W. Feit, see Zeitschr. Kryst., xxiv, 625, 1894. 



Cupeoiodaegyeite is an iodide of copper and silver, Cul. Agl, 

 described by H. Schulze from Huantajaya near Iquique, Peru, 

 where it occurs as a decomposition product of stromeyerite. It 

 is found as an incrustation or filling crevices in limestone. Color 

 sulphur-yellow ; translucent. An analysis gave : 



I 57-75 Ag 25-58 Cu 15-91 = 99-24. 

 — Zeitschr. Kryst., xxiv, 626, 1895. 



Hoefeeite is a hydrated ferric silicate closely related to 

 chloropal; it is described by F. Katzer from Kritz near Rakonitz, 

 Bohemia. It is amorphous, either earthy, granular or scaly and 

 of a bright green color; hardness 1-3 ; specific gravity 2*34. An 

 analysis gave : 



Si0 2 36-14 Fe 2 3 45-26 Al a 8 I'll ignition J8'15 = 100'66. 



This yields the formula 2Fe a O s . 4Si0 2 . 7H 2 0.— Jfin. petr. Mitth., 

 xiv, 519, 1895. 



