Sulphuret of Zinc
- Div. 1. Crystallized.
- Var. Dodecaëdral.
This substance has so many appearances, that it h of consequence 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 substance. The present, however, is not an unusual appearance of some of the massy varieties, and is representative of the primitive rhomboidal dodecaëdron, 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 dodecaëdrons may be observed. It 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 compounded 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, transparent 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.