308 Chemical Composition of the Brown Lead Ore. 
For our earliest notice of this mineral, we are indebted to Mr. 
Freiesleben, Counsellor of mines, who in his Geological Researches 
(Bd. VI. 8. 148—150) separates it from the true Brown Lead Ore, 
treating it as an appendix of that ore, and giving a complete minera- 
logical account of its properties. The collection of minerals for- 
merly belonging to Mr. Freiesleben, and now in the possession of 
the University of Moscow, contains four specimens of this mineral. 
_ These specimens are alluded to by Mr. Fischer, Counsellor of state,* 
under the name of reniform Brown Lead Ore. From whom we learn 
also, that.it had been found, before its discovery at Freyberg, at 
 Johanngeorgenstadt and at Mies in Bohemia. 
As the specific gravity of this mineral—5.836 to 6.092—is nota- 
bly lower than that of the so called, Green and Brown Lead Ore, 
which according to Mohs, in a yellowish green specimen from Jo- 
hanngeorgenstadt amounted to 7.208, in a green one from Zschopau, 
7.098, and in the variety examined by Wohler from the same locali- 
ty, as ascertained by Rose, equalled 7.054, it appeared very proba- © 
ble that there would be found to exist a difference in chemical con- 
stitution between these two minerals. And the conjecture seemed 
very probable, that the Polysphiarite might present a different satu- 
rating proportion of its constituents from the Green and Brown Lead 
Ore, or that the base of the latter might be replaced in part in the 
former, by another base specifically lighter. With a view to settle 
this point, I have subjected the Polysphirite to an acturate analy- 
sis; having for this purpose obtained of Mr. Von Weissenbach, Sur- 
veyor of mines, specimens of the most perfect purity. 
Preliminary Trials. 
Alone before the blowpipe, this mineral melts at first only upon its 
outer edges ; it then swells up, and at last, with a strong blast of the 
instrument, it melts into a white enamel-like mass. During the ex- 
periment, the flame of the candle is tinged green upon its edges: 
If small fragments of the mass are placed upon a bead of salt of 
phosphorus, and this salt is heated again, there arises a lively effer- 
vescence, and we perceive the’smell of muriatic acid. Fused with 
soda, it afforded metallic lead and a brown, semi-fused slag. No 
odor of arsenic was perceived during these trials. 
af pe ES: : * 
Muste @histoire naturelle de Puniversité Imp. de Moscow, par Fischer de 
Waldheim. Tome I, p. 297. : 
