418 Mr. Greville Williams on Emeralds and Beryls. [June 19, 



Specific Gravity of Rock-crystal after fusion. 



1W-l r\-£ nvv^pi'i _ 



ment. 



w. 



W. 



t. 



pt. 



D. 



I. 



•4116 



•2240 



o 



24 



•997367 



2-19 



II. 



•4116 



•2261 



25 



•997120 



2-21 



III. 



•4116 



•2228 



24 



•997367 



217 



IV. 



•3376 



•1832 



25 



•997120 



2-18 



V. 



•1796 



•0977 



11 



•999655 



2-19 



Mean 219 



Rock-crystal loses, therefore, no less than seventeen per cent, of 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 remains green. After fusion for a 

 short time they yield an opalescent greenish glass, which, kept for a long 

 time at the maximum temperature of the blowpipe, becomes quite transpa- 

 rent and almost colourless. 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 manner 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 (Canutillos) after fusion. 



No. of experi- 

 ment. 



W. 



W. 



t. 



pt. 



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 difference 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 



