396 Scientific Intelligence. 



ters E, F, G, H. They are distinguished from the original octa- 

 hedral faces by greater regularity and smoothness. The shape 

 and relative position of these various surfaces can be seen in the 

 diagrammatic projection depicted in the text-figure, which has 

 been drawn in the Mineralogical Laboratory of the Oxford Uni- 

 versity Museum, by the kind permission of Prof. Miers, F.R.S; 

 The drawing is to half scale. 



Description of the Surfaces. — A is an original octahedral face 

 showing typical striations, the bands varying from 0*1 to 0*4 

 centimeter, and running parallel to the edge A-E. B is a large 

 surface slightly curved showing partial striations, which, how- 

 ever, are interrupted by the slightly mammillary character of the 

 surface. C is also a natural surface showing a few striations par- 

 allel to the edge C-E. D. Between B and F, C, G, there is an 

 irregular octahedral face D, showing distinct equilateral triangu- 

 lar indentations which resemble etched figures, except in regard 

 to their comparatively large size, the largest having a side meas- 

 uring 0'1 centimeter. T> is parallel to E. 



E, F, G, H, are cleavage planes. E is the largest of these, and 

 is a very perfect cleavage plane. Parallel to it within the crys- 

 tal there is a small air layer between two internal cleavages, pro- 

 ducing a 'rainbow' or Newton's rings. F is the second largest 

 of the cleavage planes and shows a small spot within the crystal. 

 G is an irregularly shaped cleavage plane. H is another cleav- 

 age face showing series of cleavages in the corner bounded by E 

 and G. Two spots are visible, one actually on the surface, the 

 other about l cm within the crystal. Of the faces given, A and 

 G, H and B, and E and D are parallel. In the case of B and H 

 the parallelism is imperfect owing to the curvature of B. 



The purity of the crystal is best seen on looking into face E, 

 and the luster is well seen on the irregular natural face B, the 

 broken cleavage on H causing a good deal of refraction which 

 affects B to some extent as the facets of a cut gem would. For 

 a large stone the crystal is of remarkable purity, and the color 

 approximates to that of a blue-white. 



The large size of the cleavage planes E and F indicates that 

 a very considerable portion of the crystal is wanting. From the 

 shape of B, D, and G, one can say that the entire crystal was 

 irregular in shape, but A and D being octahedral faces, the pre- 

 sumption is that the complete crystal was a distorted octahedron, 

 probably with dodecahedral faces developed on the edges. The 

 portions missing probably amount to more than half of the orig- 

 inal crystal. 



The Cullinan diamond, as it has been named, after the chair- 

 man of the Premier Company, is more than three times the 

 weight of the largest diamond previously known — the famous 

 stone found in 1893 at Jagersfontein in the Orange River Colony, 

 which weighed 9 72 carats. 



4. Mo issanite, a Natural Silicon Carbide ; by George Fred- 

 erick Kunz.* — Professor Henri Moissan, at a meeting of the 



* Eead before the New York Academy of Sciences, Jan. 9, 1905. 



