173 



TAB.- CCCXCVI. 



Z 1 N C U M snlphureum. 

 Sulphur ct of Zinc, 



Div.l. Crystallized, Far. Dodecaedral. 



This substance has so many appearances, that it is of con- 

 sequence to identify some, even of the ruder-looking ones, 

 which, after the neat examples figured in tabs. 74 and 75, 

 are hardly to be recognised as belonging to the same sub- 

 stance. The present, however, is not an unusual appearance 

 of some of the massy varieties, and is representative of the 

 primitive rhomboidal dodecaedron, and the same as the , 

 fractured nucleus. It is altogether such a heap of small 

 indistinct appearances, that one can scarcely recognise 

 the parts showing what forms it belongs to ; nevertheless 

 with a little attention rugged dodecaedrons may be ob- 

 served. Tt exercises the early mineralogist in the study, 

 and stands with the more experienced as an instructive 

 lesson in the variations of Nature's school, always to be 

 esteemed for characteristics descriptive of herself. This and 

 the following figures serve to show the principal varieties of 

 crystallization, which continually form more or less com- 

 pounded forms and groups, that will occasionally combine 

 so many modifications in one, that it is very difficult to 

 comprehend them. 



There are some varieties in colour (as may be seen in a 

 slight degree), such as a fine orange brown and yellow, trans- 

 parent and brilliant, but generally in small crystals. It is 

 the resinous variety that is phosphorescent, or gives light 

 when scraped in the dark, some say with a brass pin ; but 

 I have some by favour of Mr. Pennant, from Flintshire, that 

 is so when scraped with a knife. 



This ore is often used to procure the metal from. 



TAB. CCCXCVII. 



Black Jack, as this substance is commonly called by the 

 miners, is exemplified in this specimen with the usual ap- 

 pearance, and is indeed black to a proverb, for I know of 

 no substance that has a blacker aspect. Coal is perhaps 

 even blacker when powdered, in which state Jet is brown ; 

 but this, which u full as dense and brilliant in the mass, 



