124 



which however is not quite satisfactory to me. More of this 

 will be mentioned in another place. They may be found 

 somewhat various in their colours. The most common 

 are nearly as here represented; transparent white or glassy, 

 and often pearly or greyish within; the outside being 

 coated with a light brown crust often nearly opaque, 

 which gives an idea of fresh cast wax. The fracture is 

 irregular, glassy or flinty. Analcime may be found in 

 most of these appearances so hard as to resist a knife, like 

 quartz ; but in the state of compact zeolite, or passing into 

 fibres, it may be scratched with a knife or any steel instru- 

 ment, though it resists iron and brass. 



We are not sure that this is the true hyalite of Kirwan; 

 who says it does not fuse per seat 150°. Ours fuses per se at 

 the heat which turns carnelian white, which Kirwan observes, 

 was 1 60°. 



