1835.] and Analysis of the Vanadiate of Lead. 41 



both are combinations of a salt of lead with chloride of lead. 

 Rose considers the Beresow mineral to correspond with 

 that from Zimapan. 



4. The mineral which I* am now to describe, was derived 

 from a different locality from any of those mentioned. It 

 was brought to Glasgow by Mr. Doran, an Irish mineral 

 dealer, who stated that he had procured it in an abandoned 

 lead mine in the county of Wicklow in Ireland, and is now 

 in Dr. Thomson's cabinet. 



Its colour is light brownish yellow, streak white. Com- 

 monly it appears in the form of small rounded masses or 

 spheres placed on a surface of phosphate and arseniate of 

 lead; but sometimes it is crystallized in six-sided prisms. 

 Opaque with some translucence at the edges, brittle. The 

 fracture is even or often flat conchoidal. Lustre resinous. 

 Hardness 2*75. The specific gravity I found by one trial 

 6*675, by another 6*651, which numbers approach each 

 other so nearly, that I am disposed to consider the true 

 density of vanadiate of lead to be 6*663. 



When exposed to the action of the blow-pipe on charcoal, 

 it fuses with considerable frothing into a bead, which is 

 precisely similar to the mineral itself. If the fusion is con- 

 tinued the matter spreads on the charcoal, and possesses at 

 last a dark scoriacious aspect. When the blast is continued 

 and carbonate of soda added, globules of metallic lead are 

 produced and a black scoria remains. 



With borax fuses into a bead, which is transparent and 

 red while in fusion, but on cooling it becomes suddenly 

 opaque and deep blue, when the proportion of vanadiate 

 is considerable; but emerald green if it be small. 



With salt of phosphorus in small quantity, it fuses into 

 a fine emerald green transparent glass. 



30 grains of the mineral carefully broken, and separated 

 from the substance forming the basis on which the round 

 masses were placed, were pulverized and digested in a 

 flask on the sand bath with pure dilute nitric acid. The 

 whole of the powder speedily dissolved, forming a deep 

 orange solution, with the exception of a minute portion of 

 a yellowish coloured matter, which remained in the bottom 

 of the flask. The contents of the flask were transferred 

 into a large watch glass. 



After remaining at rest for a short period the superna- 



