COLLECTION OF MINERALS. 3o5 



tiful iridescent reflexions, and the lively tints 

 which decorate their surfaces. They come from 

 the famous mines of Elba, which were worked 

 even in the time of the Romans. In the fifty- 

 first case we see several specimens of sulphuret 

 of iron, better known by the name of martial 

 pyrites : settings for stones and jewels were for- 

 merly made of it, which were called marcasites. 



The fifty-fourth case contains various speci- 

 mens of oxyde of tin, from the mine lately disco- 

 vered near Limoges. Zinc, which we see in the 

 following case, is scarcely employed for any 

 thing but alloy. There are in France several 

 mines of oxyde of zinc, which is more commonly 

 called calamine stone, or lapis calaminaris, be- 

 cause of its mixture with earthy substances. The 

 filings of zinc are of great use in fireworks, and 

 produce the brilliant stars and other beautiful 

 effects. Bismuth, which is in the fifty-sixth case, 

 also serves as alloy, and communicates its fusi- 

 bility to the metals with which it is mixed, while 

 it increases their hardness. Cobalt is used for 

 colouring glass blue, and for painting on enamel. 

 The azure blue, known by the name of smalts y 

 is prepared from this metal. 



(Fifty-seventh case.) Arsenic is well known 

 as one of the most powerful metallic poisons. 

 It is sold in its native state under the name of 



