MINERALOGY. 



533 



Oryctogao. Chemical Characters. before the blow-pipe, it is fu- 

 sible without addition into a grey semi-transparent glass 



Geotrnottic Situation. Felspar occurs in most of the 

 primitive rocks ; in many of the species of the transi- 

 tion class, and also associated with secondary and vol- 

 canic rocks. 



Uses. It is one of the ingredients in the finer kinds 

 of earthen-ware, and is said to be the substance used 

 by the Chinese under the name Petunie or Petunze, in 

 the manufacture of their porcelain. The green varie- 

 ties of felspar, which are rare, are considered as orna- 

 mental (tones, and are cut and polished, and made into 

 snuff-boxes, and other similar articles. When the 

 green varieties are spotted with white, they are named 

 Avenlurine Felspar, and are prized by collectors. 

 FIFTH SUBSPECIES. 



LABRADOR FELSPAR, Jameson Labradorstein, 



Wtrmr. 



External Character*. Most frequent colours light 

 and dark ash-grey, and smoke-grey, seldom yellowish- 

 grey. When light falls on it in determinate directions, 

 it exhibits a great variety of colours ; of these the most 

 frequent are blue and green, more seldom yellow and 

 red, and the rarest variety is pearl-grey. Occurs mas- 

 sive, or in rolled pieces; also in large, coarse, seldom in 

 small granular, very seldom in thick and straight la- 

 mellar concretions. Cleavage splendent, fracture glis- 

 tening, and the lustre intermediate between vitreous 

 and pearly. Translucent, but in a low degree. 



Chemical Characters. According to Mr. Kirwan, it 

 it more infusible than common felspar. 



Geognottic and Geographic Situations It occurs in 



rolled masses of syenite, in which it is associated with 

 common hornblende, hyperstene, and magnetic iron- 

 stone, in the Island of St. Paul, on the coast of Labra- 

 dor, where it was first discovered, upwards of thirty 

 years sgo, by the Moravian Missionaries settled in that 

 remote and dreary region. Since that time it has been 

 found in Scotland, Norway, and other countries. 



Uses. On account of its beautiful colours, it is va- 

 lued as an ornamental stone, and is cut into ring-stones, 

 snuff-boxes, and other similar articles. It receives a 

 good polish ; but the streaks caused by the edges of 

 the folia of the cleavage are frequently so prominent as 

 to injure the appearance of the stone. 

 SIXTH SUBSPECIES. 



COMPACT FELSPAR, Jameton. Dichter Feldspath, 

 Werner. 



External Characters. Colours white, grey, green, 

 xnd red. Occurs massive, disseminated, in blunt an- 

 gular rolled pieces, and in small angulo-granular con- 

 cretions ; also crystallized in rectangular four-sided 

 prisms. ^ Crystals either middle-sized, or small, and 

 always imbedded. Internally sometimes glistening, 

 sometimes glimmering. Fracture even and splintery. 

 Feebly translucent, sometimes only translucent on the 

 edges. 



3 



Chemical Characters. Before the blowpipe it melts Oryctogoo. 



with difficulty into a whitish enamel. ** , 



Constituent Parts. *>" 



Compact Felspar of Salberg in Sweden. 



Silica 68.0 Silica 51.00 



Alumina 19.0 Alumina 30.50 



Lime 1.0 Lime 11.25 



Potash 5.5 Iron 1.75 



Oxide of iron 4.0 Natron 4.00 



Water 2.5100 Water 1.2699-75 



Godon de St. Memin, Journal Klaproth, Chem. 



de Physique, t. 63. p. 60. Abhandl. s. 26'4. 



Geognottic Situation. This mineral occurs in moun- 

 tain-masses, beds and veins, either pure, or intermixed 

 with other minerals, in primitive, transition, and se- 

 condary rocks. 



Geographic Situation. The Pentland Hills contain 

 beds of compact felspar, associated with claystone, red 

 sandstone, and conglomerate. It occurs in a similar 

 situation on the hill of Tinto, and in the Ochil Hills ; 

 and associated with rocks of the same nature in the 

 Island of Papa Stour, one of the Shetland group. 



SEVENTH SUBSPECIES. 



CLINKSTONE, 'Jameson. Klingstein, Werner. Pho- Clinkstone. 

 nolith, Daubuitson. 



External Characters. Colours grey, green, and 

 brown. Occurs massive ; also in granular, columnar, 

 globular, and tabular distinct concretions. Lustre of 

 the principal fracture glistening and pearly ; that of 

 the cross fracture faintly glimmering, almost dull. 

 Principal fracture slaty, generally thick, and often 

 curved slaty, with a scaly foliated aspect ; the cross 

 fracture splintery, passing into even, and flat conchoi- 

 dal. Strongly translucent on the edges, sometimes 

 even translucent. In thin plates, it emits when struck, 

 a ringing sound. 



Chemical Characters. -It melts before the blowpipe 

 into a grey coloured glass, but is more difficultly fusible 

 than basalt. 



Const. Parti. Silica 67-25 



Alumina . 23.50 



Lime . 2.75 



Natron . 8.10 



Oxide of iron 3.25 



Oxide of manganese 0.25 

 Water . 3.00 98.10 



Klaprotk, Beit. b. iii s. 243. 



Geognottic Situation. This subspecies of felspar ge- 

 nerally contains imbedded crystals, when it forms the 

 rock named clinkstone Porphyry. It is generally as- 

 sociated with secondary trap and porphyry rocks. 



Geographic Situation. The Bass rock at the mouth 

 of the Frith of Forth, North Berwick Law, Tra- 

 prain Law, and the Girleton Hills, all in East Lo- 

 thian, and many other hills in Scotland, contain beds 

 and veins of this mineral. 



EIGHTH SUBSPECIES. 



EARTHY COMMON FELSPAR, Jameson. Aufgeloster Earthy 

 gemeiner Feldspath, Werner. common 



External Character*. Colours white and grey. flp*r- 

 Generally occurs massive, and disseminated, and some- 

 times in imbedded crystals, which agree in form with 

 those of common felspar. Internally sometimes glist- 

 ening, sometimes glimmering, or even dull. Has some- 

 times an imperfect cleavage. Fracture coarse and 

 small grained uneven, which approaches to earthy. 

 Breaks into blunt angular pieces. Either translucent 

 on the edges, or opaque. In general, it is so soft as to 

 yield to the nail : sometimes, however, it approaches 

 in hardness to felspar. Sectile, and easily frangible. 



