292 PLATINIFEROUS GREY COPPER, 

 Platiniferous Gkey Copper, Phillips. 

 A grey variet}'- of Tetraheclrite, consisting 

 of copper, lead, antimony, iron, silver, 

 platinum, and sulphur, found in Spain, with 

 ores of silver and arsenic, at Guadalcanal in 

 Estremadura. 



Platiniridium, Svanberg. A mixture of 

 platinum, and iridium in different propor- 

 tions, found in small rounded grains of a 

 silver- white colour with Platinum, in the 

 Ural, Brazil, Ava, &c. H. 6 to 7. S.G. 

 22-6 to 23. 



Analysis, from N. Taguilsk, by Svanberg : 

 Iridium . . . .76-80 

 Platinum .... 19-64 

 Palladium .... 0-89 

 Copper .... 1'78 



99-11 

 An 'alloy of platinum and iridium, in the 

 proportion of 5, 10, or 15 per cent, of the 

 latter, possesses some excellent qualities, 

 being highly ductile and easily coined. 

 Platinum. See Native Platinum. 

 Plattnerite, Haidinger. In hexagonal 

 prisms with the edges truncated: possibly 

 pseudomorphous after Pyromorphite ( Greg 

 Sf Lettsorn). Colour iron-black. 0[)aque. 

 Lustre metallic-adamantine. Streak brown. 

 Brittle. Fracture uneven. S.G. 9-4. 



Comp. Binoxide of lead, or Pb=lead 86-6, 

 oxygen 13-4 = 100. 



JBB on charcoal, easily reduced. 



Locality. It is said to have been brought 

 from Leadhills in Scotland; but it is a 

 somewhat doubtful species. 



Name. After Plattner, the Saxon che- 

 mist and metallurgist. 



PlATYOPHTHALINION, or a-XasTUOip^ocX^oV, 



(from srAaw?, broad, and c<pdc,\iu.oi, eye.) The 

 name by wdiich Grey Antimonv was known 

 to the ancients (see Stibnite), by whom 

 it was used for colouring the hair and eye- 

 brows, but principally for staining the eye- 

 lids. 



Pleonaste, Haily, Phillips. A dark or 

 pearly black variety of Iron-and magnesia 

 Spinel. Occurs in octahedrons and dode- 

 cahedrons. Opaque. Lustre splendent. 

 Fracture flat-conchoidal, S.G. 3-64. 



rig. 339. 



Comp. (Mg, Fe)AI. 



PLOMB ARSENIATE. 



Analysis, from Monzoni, by Abich : 

 Alumina .... 66*89 

 Silica . . . . . 1-28 

 Magnesia .... 23*61 

 Protoxide of iron . . . 8-07 



99-80 



Localities. Candy in Ceylon (see Can- 

 bite). Monte Somma, in Dolomite. Near 

 Kyschtimsk, in the Lral. Arendal, in Nor- 

 way, in Calc Spar on iron ore. Monzoni, in 

 the Tyrol. Bohemia. Montpellier. War- 

 wick, in New York ; and Amity, Orange co., 

 U.S. 



Name. From TrXiovaffro;, abundant ; from 

 its four facets, which are sometimes found on 

 each solid angle of the octahedron. 



When cut and polished Pleonaste is a 

 stone of consideral brilliancy. 



Brit. Mus., Case 19. 



MP. G. Upper Gallery, Table-case B, in 

 recess 6, No. 154. 



Pleuroclase, or Pleuroklas, Breit- 

 haiipt. See Wagnerite. 



Plinian, Breithaupt. A variety of Mis- 

 pickel occurring in raonoclinohedric crys- 

 tals at St. Gotthard, Ehrenfriedersdorf, 

 and Zinnwald. S.G. 6-27 to 6'46. 



Analysis, by Plattner : 



In.n .' . . . . 34-46 

 Arsenic .... 45-46 



Sulphur .... 20-07 



99-99 

 Plinthitb, Thomson. Compact. Earthy. 

 Colour brick-red. Opaque. Lustre glim- 

 mering or dull. Fracture flat-conchoidal. 

 H. 2-75. S.G. 2-35. 



Comp. 2Fe Si + 3A1 Si + 16H. 



Analysis, by Thomson : 



Silica 30-88 



Alumina . , . . 20-76 

 Protoxide of iron . . . 26-16 



Lime 2-60 



Water 19-60 



100-00 



BB alone, infusible, but turns black. 



Localities. — Irish. Down Hill, co. An- 

 trim, and at the Little Deer Park near 

 Glenarm, in reddish ti-ap-rock. 



Name. From TzXlvdo;, a brick or tile; in 

 allusion to the colour. 



Plomb Antimonie Sulfure. See Bou- 

 langerite. 



Plomb Arseniate, Haily. See Mime- 



TITE. 



