COLLECTION OF MINERALS. 2g5 



and hardness. The first is the zircon, a fine series 

 of its crystals is to be seen on the stage for 

 study. The precious stones, furnished by this 

 mineral, are the jar goon of Ceylon, which is of a 

 greenish yellow, or a marigold hue, and the hya- 

 cinth scarlet mixed with brown. 



The next case presents the corundum, which 

 of all minerals is the most rich in precious stones. 

 Those called ruby, topaz, and oriental sapphire, 

 by jewellers, are only varieties of this substance ; 

 one of which is red, another yellow, and a third 

 of an indigo blue. In the collection for study 

 we find prismatic and pyramidal crystals of 

 these different colours, and afterwards speci- 

 mens, polished, but not cut, of similar crystals ; 

 one of them is divided into* two parts, one red, 

 the other yellow, so that it is at once a ruby and 

 a topaz ; which circumstance is the best proof, 

 that the colour of these stones is merely acci- 

 dental, and cannot affect their nature. By the side 

 of the transparent variety, of which we have for- 

 merly spoken, we see others which are more or 

 less opaque, and extremely lamcllated : for which 

 reason they have been named, by M. Haiiy, har- 

 mophane; their former name was adamantine 

 spar. The last variety, less remarkable in appear- 

 ance, is the granulated corundum, vulgarly called 

 emery, the fracture of which is compact and 



