ORDER IV. TETARTO-PRISMATIC VITEIOL-SALT. 47 



Surface. P-f oo sometimes, f r -f oo almost always, 

 vertically streaked. The rest of the faces smooth 

 and even. 



Lustre vitreous. Colour white, sometimes inclin- 

 ing to peachblossom-red, and violet-blue, pale. 

 Streak white. Transparent ... translucent. 



Brittle. Hardness = 2-0 ... 2-5, Sp. Gr. = 2-036. 

 Taste astringent, nauseous and metallic. 



Compound Varieties. Reniform, botryoidal, sta- 

 lactitic ; composition columnar, if the particles be 

 very delicate, the lustre becomes pearly. Massive : 

 composition granular passing into impalpable. 



OBSERVATIONS. 



The prismatic Vitriol-salt from the Rammelsberg, near 

 Goslar, consists of 



Oxide of Zinc 27-5. 



Oxide of Manganese 0-5. 



Sulphuric Acid 20-0. 



Water 50-0. KLAPROTH. 



According to MITSCHERLICH its chemical formula is 

 Zn S* + 14 Aq, corresponding to 27'67 Oxide of Zinc, 

 27'57 Sulphuric Acid, and 44-76 Water. It is very easily 

 soluble in water ; before the blowpipe it froths, and covers 

 the charcoal with a white coating. 



2. It seems that the decomposition of dodecahedral Gar- 

 net-blende gives rise to the formation of the present spe- 

 cies, though in general that species be not very subject 

 to be decomposed by the action of the atmosphere. Its oc- 

 currence in nature corresponds to the mode of its formation. 



3. It is found in the Rammelsberg near Goslar in the 

 Hartz, at Schemnitz in Hungary, at Fahlun in Sweden, 

 at Holywell in Flintshire, and it is said also in Cornwall. 



4. It occurs but sparingly in nature, but is often pro- 

 duced artificially by chemical processes. It is employed 

 in medicine, but its principal use is in dyeing. 



