336 EARTHS PROPER. 



rect. Indeed, neither Klaproth nor Vauquelin 

 succeeded in freeing the zirconia completely 

 from iron. But if we deduce the atomic weight 

 of zirconia from these analyses, supposing the 

 minerals to be simple silicates of zirconia mixed 

 with a little silicate of iron, then the atomic 

 weight of zirconia will be as follows : 



From first analysis 5-247 



From second 3 -9 8 7 



From third 4-043 



From fourth 5-645 , 



From fifth 4-134 



From sixth 4'370 



6)27-426 



Mean - 4-537 



A careful examination of a collection of hya- 

 cinth crystals, which I was favoured with some 

 years ago by Mr. Heuland, serves, in some 

 measure, to explain the reason of these anomalies. 

 Besides crystals of zircon, I found among them 

 likewise crystals of spinel!, garnet, quartz, and 

 some green fragments having the colour of 

 emerald, besides some black grains, apparently 

 octohedral iron ore. It was doubtless owing to 

 the presence of some of these foreign crystals 

 that the alumina, which I observed in a former 

 analysis of the hyacinth, is to be ascribed. Pure 

 and regular crystals of hyacinth seem composed 

 of 



16 



