78 Diwovery of the VauqudinvU. 



his analysis of the r, ,1 1 ad ore of 8ih ria* (the ore in which 

 chromium was discovered by that celebrated chemisl : but he 

 dot- • appear bo have regarded it as a distinct - 

 Cleaveland places it as a sub-species, after the chromate of lead. 

 It v rt, I believe, raised to the rank of a species by 



'• Dnard,and adopted by Berzelius, who notices it in his essay 

 on tlic blowpipe, under the name of Vauquelinite. Most of the 

 mod, tii writers on mineralogy, consider it as distinct, both in 

 chemical and physical characters from the red ore of chronic, f 

 In the Bystem of blohs, Vauquelinite is still placed in the ap- 

 pendix which contains thejproposed species, or such as an? not 

 Btablished. It must occupy this place in any system 

 based on physical characters alone, until its crystalline form 

 can be clearly determined; and unfortunately it has hitherto 

 only been found, cither massive, or in crystals so microscopic, 

 that they cannot be submitted to the goniometer.! 



The Vauquelinite is one of the rarest minerals known. Not- 

 withstanding it ih nearly forty years since it was discovered, 

 there is but one undoubted locality of it recorded : this is the 



♦ This mineral is not a diehromate as Btated by Turner, (ed. 5. p. 570,) but 



pound identical with tin- ordinary artiticial clirome yellow. It is only red 



in a crysi;i)lii t when reduced to powder, like the red 



chra potassa, and some other red crystalline matters. When it was more 



abundant it \ d as a yellow, not as a red pigment There is, however, 



lining with the redkado •, a disttnd species, lately determined 



[ermann, and calk-d by him Melanochroite. It is crystallised, and its pow- 



dcri- d colour. I»r. Thomsoo | I . L. p. 661) 



■;-'1h ii ns ;i Subsesquichromab of Lead. 



f Dr. Thomson (L a p. 61* Vauquelinite is a compound of two 



atoms of chromate of lead, and one atom of oxide of copper; but Berzelius 



calls it chromate plwmbu .« ■ 1 his 



mpositioD is probably correct Thi obtained by the analy- 



i Berzeli 



Chromic acid . - • - 28 



Protoxide of Lead - - I 



• Oopper - - - id. mi. 



* ! aerely phosphate of lead. 



i . .'■'in. 



