Mr. Grevillc Williams on Emeralds and Beryls. 323 



its specific gravity on passing from the crystalline to the amorphous 

 state, or about a half per cent, less than is undergone by garnets, 

 according to the observations of Magnus ; whereas the beryl A only 

 lost nine per cent., or little more than half as much. 



On the Effects of Fusion upon Emeralds. — On heating alone before 

 the oxyhydrogen blowpipe, these emeralds bear a bright red heat 

 without losing their colour ; and at a heat which causes incipient 

 fusion, the edges turn colourless and opaque, while the centre re- 

 mains green. After fusion for a short time they yield an opalescent 

 greenish glass, which, kept for a long time at the maximum tempe- 

 rature of the blowpipe, becomes quite transparent and almost colour- 

 less. The addition of chromic oxide causes the bead to become of a 

 dull green colour, which is not improved by moderate heating. The 

 fact that emeralds endure a temperature capable of fusing the edges 

 without the centre losing colour, appears conclusive against the 

 idea of the colouring-matter being organic. The beads produced 

 by the fusion of emeralds resemble those formed in the same man- 

 ner from beryls ; the phenomena during the fusion are also nearly 

 alike ; but it takes longer and a higher temperature to produce a 

 colourless transparent bead with emeralds than with colourless 

 beryls. The beads can be scratched by quartz ; and the density is 

 reduced to the same extent as with the beryl. 



Specific Gravity of Emeralds (Oanutillos) after fusion. 



No. of experi- 

 ment. 



W. 



W. 



t. 



pi. 



D. 



I. 



•7432 



'4334 



o 



13 



•999430 



2-40 



The density of fused emeralds is therefore almost exactly the 

 same as the globules obtained in a similar manner from the beryl A. 



Beryls, from the most various sources and of the greatest differ^ 

 ence in appearance, vary but little in specific gravity : thus a large 

 crystal of beryl from Haddam County, North America, weighing 

 1089 grms., had its specific gravity determined by suspension ; and 

 the number obtained was 2*67. The beryl A from Ireland gave 

 2' 66; and a beautiful transparent yellow crystal, the locality of 

 which is doubtful, gave 2*69, or exactly the same as the emeralds 

 from Santa Be. 



On the Effects of Fusion upon an Artificial Mixture of Beryl In- 

 gredients. — Being desirous of trying the effects of fusion upon an 

 artificial mixture of the same composition as that of a beryl, I 

 made a series of careful analyses of the beryl A. The results of 

 these analyses have led me to a laborious examination of the pro- 

 cesses at present in use for the separation of alumina from glucina. 

 The study of the original carbonate-of -ammonia process of Vau- 

 quelin, and the modifications of Bose, Joy, Hofmeister, and others, 

 has taken twelve months of constant work ; but even my earlier 

 analyses enabled me to obtain a sufficiently close approxima- 

 tion to the composition of the bervl A. The following were the 



Z2 ■ 



