145 



Phil. Trans, for 1802, 323. where quoting Hauy, v. 4. 562. 

 who observes " that it scratches quartz ; that its specific 

 gravity is 3'l65, and that it is infusible by means of the 

 blowpipe ;" Bournon observes, " that it is red with a 

 purplish tinge*; that the appearance of the substance was 

 entirely different from that of felspar ; and that where it 

 came in contact with the felspar it seemed to mix itself 

 with it in such an insensible manner, that after having 

 sawed and polished a piece composed partly of felspar and 

 partly of the substance here spoken of, it was impossible by 

 the eye to distinguish exactly where the felspar began, or 

 where the other substance terminated." Ours is readily di- 

 stinguished from felspar, which it invests occasionally so 

 that it is formed round it like a tube, see the middle figure 

 at the lottom : it is also often running among it in the di- 

 rections of the fragments, often passing abruptly across it. 

 The nearest approach to mixing insensibly is by fibres, 

 which in ours are however sufficiently distinct. The Count 

 continues to observe, fi that the pieces he had collected 

 varied considerably in their degree of hardness, although 

 all of them were harder than felspar usually is, for many 

 of these pieces would scarcely scratch felspar; whereas others 

 could scarcely be scratched by the greatest number of gems, 

 or precious stones. The characters of the last-mentioned or 

 hardest pieces appeared to be very similar to those of the 

 imperfect corundum from China, a crystal of which Rome 

 de Lisle had sent him a short time before. The above obser- 

 vations, joined to the remarkable manner in which this sub- 

 stance was mixed with the felspar, made him adopt the er- 

 roneous opinion mentioned by the abbe Hauy in his obser- 



* Some of ours are also of a greenish tinge, especially when between the ey 

 and the Heht. 



