150 PHYSIOGRAPHY. CLASS II. 



nation 6f the axis in the plane of the long diagonal = 5 45'. 

 Cleavage parallel to P <x> very perfect, and . Sur- 

 face generally smooth and shining, some of the faces rough. 

 It occurs also in twin-crystals. . Lustre adamantine. Co- 

 lour deep and beautiful azure-blue. Streak pale-blue. 

 Faintly translucent. Rather brittle. Hardness = 2 '5 ... 

 3-0. Sp. Gr. = 5-30 ... 5-43, BROOKE. 



It consists of 74'4 sulphate of lead, 18 'oxide of copper, 

 and 4'7 water, according to Mr BROOKE. The locality of 

 this species is Leadhills, where it occurs along with the pre- 

 ceding ones. It has also been found at Linares in Spain. 

 It was discovered by Mr SOWERBY, and described as car- 

 bonate of copper in his British Mineralogy ^ III. 5. 



iv. Corneous Lead. 



Corneous Lead. JAM. Syst. Vol. II. p. 388. Man. p. 468. 

 Murio-carbonate of Lead. 



Pyramidal. Combinations like Fig. 101., having the sum- 

 mit replaced by a plane perpendicular to the axis. Incli- 

 nation of s to g = 135, BROOKE. Cleavage parallel to 

 P + os, cross-fracture conchoidal. Lustre adamantine. Co- 

 lour white and pale tints of grey, yellow, and green. Streak 

 white. Transparent... translucent. Rather sec tile. Hard- 

 ness below 3-0, inferior to that of di-prismatic Lead-baryte. 

 Sp. Gr. = 6-056, CHENEVIX. 



According to KLAPROTH it consists of 85-5 oxide of lead, 

 8-5 muriatic acid, and 6-0 carbonic acid. Before the blow- 

 pipe it melts quickly into a yellow globule, which becomes 

 white, and crystallises upon the surface, when cooling. 

 Upon charcoal it is reduced. The localities of this mineral 

 are Matlock in Derbyshire, Hausbaden near Badenweiler 

 in Germany, and Southampton in Massachusetts, North 

 America. It is found with other ores of lead, with octa- 

 hedral Fluor-haloide, prismatic Hal-baryte, &c. 



