298 POLYHYDRITE. 



PoLYHYDRlTE, Breithaupt. See HlsiN- 



GERITE. 



PoLYKRASE, Scheerer. See Polycrase. 



PoLYLiTE, Thomson. A variety of Pyr- 

 oxene, nearly related to Hedenbergite, 

 occurring in plates Avith a lamellar struc- 

 ture and a cleavage in one direction. Colour 

 black. Opaque. Lustre vitreous. Brittle. 

 H. 6 to 6-5. S.G. 3-23. 



Co7np. (Fe, Ca, Mn)^ (2 Si Al). 



Analysis, by Thomson : 



Silica . . . . .40-04 

 Alumina .... 9*43 

 Protoxide of iron . . . 3408 

 Protoxide of manganese . 6-60 

 Lime ..... 11-54 

 Water ..... 0-40 



102-08 

 JBB alone, infusible ; with borax fuses to 

 a black glass. 



Locality. Hoboken, in New Jersey, form- 

 ing a bed about a ^ incti thick in Magnetic 

 Iron Ore. 



Name. From ^-oAl?, many, and >~i6og, stone, 

 in allusion to the numerous constituents of 

 which it is composed. 



POLYMIGNITE, Berzelius. Rhombic. Oc- 

 curs in long thin prisms, generally striated 

 longitudinally, and with the edges replaced. 

 Colour black. Opaque. Lustre submetallic, 

 but brilliant. Streak dark brown. Fracture 

 conchoidal. H. 6-5. S.G, 4-77 to 4-85. 

 Comp. Titanate ofZirconia. 

 Analysis, by Berzelius : 

 ' Titanic acid .... 46-30 

 Zirconia . . . . 14-14 

 Yttria ..... 11-50 

 Peroxide of iron . . . 12-20 

 Peroxide of cerium . . 5-00 



Lime 4-20 



Peroxide of manganese . 2*70 

 Potash, magnesia, silica, and 



oxide of tin . . . traces 



96-04 



BB alone, infusible and unchanged ; with 

 borax fuses readily to a glass coloured by 

 iron ; with tin to a yellowish-red globule. 



Soluble in sulphuric acid. 



Locality. Fredericksvarn, in Norway, in 

 zircon-syenite, in crystals sometimes up- 

 wards of an inch long. 



Name. From ^oxh;, much, and i^iywfx.t^ to 

 mix, in allusion to the number of its com- 

 ponents. 



Brit. Mus., Case 37. 



PoLYSPH^RiTE, Breithaupt. A botryoidal 



PORCELAIN SPAR, 

 variety of Brown Lead Ore (see Pyro- 

 morphite), containing phosphate of lime, 

 as well as a certain quantity of. fluoride of 

 calcium. Structure radiated internally. Co- 

 lour brown or yellow ; slightly darker than 

 Pyromorphite. Lustre greasy. Fracture con- 

 choidal. S.G. 6-9 to 6-1. 

 Analysis, by Kersten : 



Phosphate of lead . .77-02 

 Phosphate of lime . . 11-05 



Chloride of lead 

 Fluoride of calcium 



. 10-84 

 . 1-09 



100-00 

 Localities. The mines of Sonnenwirbel 

 and St. Nicholas, near Freiberg, in Saxony. 

 Name. From ^oxhs, many, and trcpKi^o?, 

 sphere, in allusion to its occurrence in round- 

 ish masses. 

 Brit. Mns., Case 54. 



Polystomous Augite Spar, Keating. 

 See Jeffersonite. 



PoLYTELiTE. The name given by Glocker 

 to varieties of Grey Copper (Tetrahedrite), 

 containing silver and quicksilver. 



Name. From ■^roXtnXy,;, valuable, because 

 of the large amount of silver it contains. 



PoLYXENE, Hausmann. See Native 

 Platinum. 

 Ponce, Beudant. See Pumice. 

 PooNAHi.iTE, Brooke. A variety of Scole- 

 cite, occurring in slender rhombic prisms 

 and radiated fibrous masses, resembling 

 Needlestone.. Colour white. Lustre pearlv. 

 H. 5 to 5-5. 



Analysis, by Gmelin .• 



Silica 45-12 



Alumina .... 30-44 

 Lime . . . . . 10-20 

 Soda, with a trace of potash . 0-66 

 Water 13-39 



99-81 



Locality. Poonah, in Hindostan, associ* 

 ated with Apophyllite, and forming with it 

 large kidney -form masses, in amygdaloid. 



Brit. Mus., Case 28. 



M. P. G. Horse-shoe Case, No. 1174, 

 from the Railway Tunnel, Bhore Ghaut, be- 

 tween Bombay and Poonah. 



Porcelain Clay, Kirwan. > See 



Porcelain Earth, Jameson. \ Kaolin. 



Porcelain Jasper, or Porcellanite. 

 Clay altered by heat, and often having the 

 aspect of certain kinds of porcelain. 



Porcelain Spar. Porcelan-spath, 

 Dufrtnoy. Porcellan-spath, Fuchs. Oc- 

 curs in rhombic prisms ; also massive land 

 coarsely granular. Colourless or pale- grey. 



