302 PROTHEITE. 



Name, from ■n-^cc-u^i^ov^ a mask; in allu- 

 sion to its deceptive or masked condition. 



M. P. G. Horse-shoe Case, No. 366. 



Protheite, Dufrenoy, or Protherite, 

 Ure. A variety of Idocrase from Zillerthal, 

 in the Tyrol. Occurs in rectangular 

 prisms, with the faces striated longitudinally. 

 Colour olive-green or white. The smaller 

 specimens translucent, the larger nearly 

 opaque. 



Protoxide of Uranium. See Pitch- 

 blende. 



Proustite, Beudant, Dufrenoy ; or 

 Light-red Silver Ore. 'Hexagonal : 

 primary form an obtuse rhombohedron. 

 Colour cochineal- to crimson-red. Sub- 

 transparent to translucent at the edges. 

 Lustre adamantine. Streak cochineal-red. 

 Sectile. Fracture conchoidal to uneven. 

 H. 2 to 2-5. S.G. 5-42 to 5-56. 



Camp. Sulphide of silver and arsenic, or 

 Ag3 S + As S^ = sulphur 19*4, arsenic 15'2, 

 silver 65-4=100. 



Analysis, from Joachimsthal, by H. Rose : 

 Sulphur . . . .19-51 

 Arsenic .... 15-09 

 Silver ..... 64-67 

 Antimony . . . . 0"69 



99-96 



BB fuses, giving oflF arsenical fumes; 

 ultimately on charcoal yields a globule of 

 silver. 



Localities. Johanngeorgenstadt, Marien- 

 berg, and Annaberg, in Saxony. Joachims- 

 thal, in Bohemia. Baden, Alsace. Guadal- 

 canal, in Spain. Mexico. Peru. 



Name. After J. L. Proust, the French 

 chemist. 



This is a valuable ore of silver. See 

 Pyrargyrite. 



31. P. G. Principal Floor, Wall-case 22. 



Prunnerite. a greyish-violet coloured 

 calcareous tufa, found in Faroe. 



Pryan (from Pryi, clay, Cornish'), 

 Pryan Ore, Pryan Tin, Pryan Lode. 

 That which is productive of Copper Ore or 

 Tin, but does not break in large solid stones, 

 only in gross pebbles, or sandy with a mix- 

 ture of clay. {Pry re.) 



The word Pryan is now generally given 

 to a white, fine, somewhat friable clay. 



Przibramite, Huot. Cadmiferous Blende, 

 from Przibram in Bohemia. The same name 

 has also been given to the capillary variety 

 of Gothite (Sammetblende), which occurs at 

 that locality. 



PsATHYRiN, Glocker. See Hartine. 



Psaturose, Beudant. Colour dark lead- 



PSILOMELANE. 



grey, inclining to iron-black. Streak black. 



H. 2. S.G. 6-275. 



Comp. Sulphantimonite of silver, or 6Ag, 



S + Sb S3 = silver 70-3'3, antimony 14-Oi, 



sulphur 15-63 = 100. 



Analysis, from Schemnitz, by H. Rose : 

 Silver . . . . . 68-54 

 Antimonv .... 14-68 



" Copper." .... 0-64 

 Sulphur .... 16-42 



100-28 



BB on charcoal fuses readily, forming a 

 white film, sometimes also giving out an 

 odour of arsenic : yields a globule of silver in 

 the outer flame. 



Easily soluble in hot nitric acid, with 

 separation of sulphur and antimonic nitrate. 



Localities. Shemnitz, in Hungary. Frei- 

 berg, in Saxony. Zacatecas, in Mexico. 



Name. From ■^a.Qv^b?, fragile. 



Pseudo-Adamantes, or Mock Dia- 

 monds. A name for Cornish Diamonds, 

 and similar limpid Rock Crystal from 

 other localities. 



Pseudo-Albite. See Andesine. 



Pseudo-Apatite, Breithaupt. An impure 

 Apatite, affected by decomposition ; from 

 the Kurprinz mines at Freiberg, in Saxony. 



PsEUDO- Diamond. Transparent and 

 colourless Rock Crystals, cut and polished. 



Pseudo-Malachite, Hausmann. See 

 Phosphochaj.cite. 



PSEUDOMORPHOUS PyRITES. Is fouud 



at Alston, in Cumberland, in cubes after 

 Fluor ; near Tavistock, in Devonshire, in flat 

 hexagonal crystals after Calcite; also at 

 Herodsfoot Mine and Huel Mary,in Cornwall. 



Pseudo-Nepheline. See Nepheline. 



Pseudo-Saphir. See Cordierite. 



PsEUDO-SoMMiTE. Lcucitc changed bv 

 alteration to Glassy Felspar, has been ob- 

 sei-ved by Scacchi on Somma. 



Pseudo-Triplite. a form of Triplite 

 which has undergone alteration by taking 

 up water, and the protoxides passing to 

 peroxides. 



Comp. (#e, 5tn)5 P2 + 2H. 

 Analysis, from Bodenmais, by Delffs : 



Phosphoric acid . 



. 35-71 



Peroxide of iron . 



. 51-00 



Peroxide of manganese 



. 8-07 



Water .... 



. 4-52 



Insoluble 



. 0-70 



100-00 

 Locality. Bodenmais, in Bavaria. 

 PSILOMELANE, Phillips, Nicol. PsiLO- 

 melanite, Thomson. Am.orphous. Massive, 



