METALS. 87. Plumbum. , 281 



-Found in Cornnvally De'VOftJhire^ the Scilly ijlands^ Indiay Bo- 

 hernia^ ^axony^ SitefiOy Sec, in mafTes or rounded pieces: 

 colour dark or hlackifli-brown with various fhade.'! of yellow- 

 ifli or afhy-grey or browhifh red : it is very hard, decrepi- 

 tates before the blowpipe, and on charcoal is partly reduced: 

 it tinges borax white: fpecific gravity from 6,goo. to 6,970. 

 contains tin 77,50. oxygene 21,50. iron 00,25. filica 00,75. 



erystallinum Compadl, opake, ponderous, with a light grey flreak, in 



the form of cryftals. 



Stannum tefieriscrylt. Syft, nat, xii. 3. p. 130. «, 1,2. 



Stann. arfenico < rylL Wall, fyst, 2. p. 320. n. 2, 3, . 



Common tinilone. Kifwan miner. 2 p. 197. 



Brown tinftone. Schmetjser miner- 2. /. 160. • 



Tinrtone. Thomfon chem, 4. p. 68. 



Oxygenized tin, Sr,cwerby Brit, miner, t, i?. 80. 81. 82. 85. 



Pound in all tin mines, (ometimes very fmall and cluftered 

 together, fometimcs in larger regular cryftals : colour black 

 or brown with g-^nerally a fhining furface, rarely red, yeU 

 ^owifh, or green fli : they are found interfperfed in quartz, 

 fluor, or other matrices, or loofe among the foil or fand : the 

 cryftals are very irregular, the primitive form of which is 

 fuppofed to be a cube, Kut they commonly occur in the form 

 oi double or fingle 4-fided pyramids with the edges bevilled. 



87. PLUMBUM. Blulfli-white gradually black- 

 ening in the air, loft, very malleable, a little 

 dii6lile and tenacious, not fonorous, ftaining the 

 fingers of a bluifh colour, fpecific gravity 1 1,352: 

 eafily itk king exhibiting iridefcent colours on the 

 furface during liquefadlion, and becoming firft a 

 white, then a grey, then a yellow, and laflly a red 

 * oxyde, all of which are eafily convertible into 



glafs : foluble in all acids and giving the (olution 

 a fweetifh tafle, precipitating a yellow powder if 

 dilTolved in nitric acid and potafs be added to the 

 fblution. Lead, 



nati'vunu Uncombined. 



Plumbum nudum, ^yft. nat, i, p. 180. », i. 

 Plumbum nativum. Wall. mmer. 272. 



VOL. VIT. — N n 



