X LEAD. 287 



secondary forms are given on the same plate, fig. b, c, and d. 

 The crystals are small, often long and acicular ; also broad and 

 tabular. It varies from translucent to transparent, and it refracts 

 double in a high degree ; the fracture is small conchoidal, and the 

 lustre resinous or adamantine. It is brittle, and very easily fran- 

 gible. The specific gravity is'6'72. Before the blow-pipe, it 

 decrepitates and mefts into a metallic globule. It consists of, 

 oxide of lead 82, carbonic acid 16, water 2=100. — Klaproth. 

 This ore occurs in small quantities in several of the English lead 

 mines. 



Sp. 4. Phosphate of Lead, or Green Lead-Ore. Pl. XL. 

 fig. 2. — Grun bleierz, Werner; Plomb phosphate, Hauy, — Its 

 colours are various shades of green, yellow, and white. It seldom 

 occurs massive ; sometimes stalactitic, reniform, and botryoidal ; 

 but most commonly crystalized in the form of a six-sided prism, 

 fig. e; variously modified, fig./*, g, and h. The crystals are small, 

 super-imposed, and sometimes form velvetty or mossy-like drusy 

 crusts. They are smooth and shining, or splendent, externally ; 

 internally, glistening, and the lustre is resinous. It is more or less 

 transparent, brittle, and easily frangible. The specific gravity is 

 6'4. It dissolves in acids without effervescence. It contains, 

 oxide of lead 80, phosphoric acid 18, muriatic acid 1*62. — 

 Klaproth. It occurs along with galena and other ores of lead in 

 the northern counties of England ; and also in Scotland. 



Sp. 5. Arseniate of Lead. Pl. XL. fig. 3. — Plomb arsenie, 

 Hauy. — The prevailing colours are pale-yellow and green. It 

 occurs massive, in granular concretions, in small acicular six-sided 

 prisms, or in' very delicate capillary silky fibres, which are trans- 

 parent, slightly flexible, and easily frangible. The specific gravity 

 is 5*0, 6'4. Its constituent parts are, oxide of lead 69"76, arsenic 

 acid 26 - 4, muriatic acid 1*58. — Gregor. It is found in the mine 

 of Huel Unity, in Cornwall ; also at St. Prix, in France. Reni- 

 form Arseniate of Lead is of a reddish -brown colour, and has 

 hitherto been found only in Siberia. Earthy Arseniate of Lead 

 has a yellow colour, and occurs in crusts along with filamentous 

 arseniate of lead, at St. Prix. 



Sp. 6. Chromate of Lead. Pl. XL. fig. 4. — Rotlr Bleierz, 



