278 PEPJCLINE. 



Periclinb, P/^^//^ps. PeRIKLIN, Breit- 

 haupt. A variety of Albite, in which a por- 

 tion of the soda is replaced by potash. In 

 twins like those of Albite. Generally more 

 opaque, and of less specific gravity, than 

 ordinary Albite or Felspar. H. 6. S.G. 2-64. 



Fig, 324. 



Fig. 325. 



Comp. (Na, K + Al) Si^. 



Analysis, from Pantellaria, by Abich : 



Silica 68-23 



Alumina .... 18-30 

 Peroxide of iron . . . I'Ol 



Soda 7-99 



Potash 2-53 



Lime ..... 1-26 

 Magnesia . . . .0-51 



99-83 



J5B fuses more readily than Albite. 



Localities. St. Gotthard, in Switzerland, 

 in large distinct crystals. Zoblitz, in 

 Saxony. The Pfundersthal and Schmierner- 

 thal, in the Tyrol. The Sau-alpe,in Carinthia. 



Name. From ^ipiy.xiyvis, inclined about (the 

 end). 



Brit. Mus., Case 30. 



Peridot, HaUy; Peridot-olivine. See 

 Chrysolite. The name Peridot is derived 

 from the Arabic /er/c?e^, a precious stone. 



Peridot Blanc, Scacchi. Translucent, 

 white, or colourless Chrysolite, from Vesu- 

 vius. See MONTICELLITE. 



Peridot Granuliforme, Hauy. See 

 Olivine. 



Peristerite, T. S. Hunt. A variety of 

 Albite containing disseminated grains of 

 Quartz, or in fine cleaveable masses free 

 from Quartz. Lustre vitreous. Exhibits a 

 fine play of colours analogous to that of 

 Labradorite. H. 6. S.G. 2 625 to 2-627. 

 Analysis, by T. S. Hunt: 



Sifica 66-80 



Alumina .... 21-80 

 Peroxide of iron . . . 0-30 

 Soda ..... 7-00 

 Potash . . . . .0-58 



Lime 2-52 



Magnesia .... 0-20 

 Loss by ignition , . . 0-60 



99-80 

 Locality. Bathurst, in Canada. 



PEROWSKITE. 



Name. From ^sfis-TE^a, a pigeon, from the 

 resemblance of its colours to those on a 

 pigeon's neck. 



When cut in a proper direction, Peri- 

 sterite exhibits a delicate celestial-blue opal- 

 escence, which is very beautiful. 



Peritomous Antimony Glance, Mohs. 

 See Freieslebenite. 



Peritomous Augite Spar, Mohs. See 

 Arfvedsonite. 



Peritomous Hal-baryte, Mohs. See 

 Strontianite. 



Peritomous Kouphone Spar, Mohs. 

 See Mesotype. 



Peritomous Lead Baryte, 3Iohs. See 

 Mendipite. 



Peritomous Ruby Blende, Mohs. See 

 Cinnabar. 



Peritomous Titanium Ore, Mohs. See 

 Rutile. 



Perlaire, Haiiy. PERLiT,or Perlstein, 

 Werner. See Pearlstone. 



Perlglimmer, Leonhard. See Marga- 



RITE. 



Perl-stein, Werner ; or Pearl- Stone, 

 Jameson. When felspathic rocks have un- 

 dergone perfect fusion, those portions of the 

 mass which have cooled the least rapidly 

 assume the form of Pearlstone. This has 

 a pearly lustre, inclining to waxy, and is of 

 various tints of grey, yellow, brown or red. 

 It is translucent at the edges or opaque, and 

 has a small-conchoidal fracture. H. 6. S.G. 

 2-25, to 2-38. The material {Fitchstone) 

 forming the paste or main mass of the rock, 

 contains rounded or completely spherical 

 nodules of a clear grey colour, and easily 

 detached from the matrix. These have been 

 compared to pearls, and have given the 

 name of Pearlstone to the rock, while the 

 kernels in question have received the name 

 of Spherulite, from their spherical shape. 



BB swells up violently, and forms a 

 white, spongy slag. See Obsidian. 



Brit. Mus., Case 31. 



M. P. G. Upper Gallery, Wall-case 1, 

 Nos. 48 to 55 ; Wall-case 2, Nos. 14 to 25. 



Perofskite, G. Rose. See Peroavskite. 



Perowskine. See Tetraphyline. 



PERO\vsKiTE,^e/m^oit. First discovered 

 by Butzengeiger in the granular limestone 

 of Vogtzburg, on the Kaiserstuhl, and de- 

 scribed by Walchner in 1825. Crystallizes 

 in cubes and individual crystals, made up 

 of an aggregation of smaller cubes, between 

 which there are sometimes delicate films of 

 Calc Spar, as may be ascertained by treat- 

 ment with acids.* Cleavage very distinct, 

 parallel to the faces of the cube. Colour 



