M I N E R A L O G Y. 



535 



Oryctogno- into acids, it zelatinates. Before the blowpipe it melu 



y- into a milk-white enamel. 



< ">"-' Constituent Parti. Silica, . 44.00 



Alumina. . 34.00 

 Lime, . . 0.12 

 Potash and Soda, 16.50 

 Oxide of Iron, 4.0098.62 



yautjuelin, in Hu'uy's Tabl. Comparative, p. 178. 



Geegnoilic and Geographic Silitatmu. The blue 

 variety is found at Laurwig, and the red at Stavem and 

 Friedrichswarn, both in the rock named zircon syenite. 



U*e*. The pale-blue variety, which has often an 

 opalescence like that of the adufaria-moonstone, is cut 

 m cabochon, and used for ring- stones. When set, it is 

 difficult to distinguish it from cat's-eye. 



Observations. Few of the newer mineral species 

 have bad so many names given to them as Scapohte, as 

 appears from the following enumeration : 1 . Pnrnnthine ; 

 2. Wernerite ; 3. Arcticite ; 4. Sodaite ; 5. Natrolitc ; 

 6. Fuscite ; Gabbronite ; 8. Elaolite ; 9. Fettstein ; 

 10. Lythrodes; 11. Spreustehi ; 12. Bergmannite. 

 Chintoi.ic. * CiiiA'TOLiTE, Jameson. Hohlspath, Werner. 



External Character*. Colours white and grey ; the 

 white colours yellowish- white, greenish- white, greyish- 

 white, and reddish-white ; grey colour* pearl-grey, 

 gremish-grey, and yellowish-grey. Occurs always 

 crystallized. Primitive form appears to be an oblique 

 Miteil prism, with lateral edges of 84 48', and 

 'J5 12'. The following are the secondary forms : 



1. Four-sided prism, in which the lateral edges are 

 rounded, f . Four prism* arranged in the form of a 

 cross. 



These crystals always appear as if they had been at 

 one time hollow, and these hollows filled up with clay- 

 slate, the poaition of which varies in regard to the 

 crystal*. Cleavage double, and in the direction of the 

 lateral planes of the prism. Lustre of the cleavage 

 glistening, that of the fracture glimmering. Fracture 

 splintery. Translucent. Hard; scratches glass. Rather 

 difficultly frangible. Sp.gr. 2.944, Haiiy. 2.923, Kanrten. 



Chemical Character*. It is infusible before the blow- 

 pipe, and becomes white and nearly opaque. 



It* constituent parts have not as yet been ascertained. 



Geognoslic and Geographic Situation*. It occurs in 

 small acicular crystals in clay-slate in Wolfscrag near 

 Kcswick, and near the summit of Skiddaw in Cumber- 

 land ; also at Aghavanagh, and Baltinglas-hill, in the 

 county of Wicklow. The largest and most beautiful 

 crystals are found in clay-slate near to St. Brieux in 

 Brittany ; smaller crystals occur in the clay-slate of St. 

 Jago di Compostella in Gallicia. 



Observations. Chiastolite is placed immediately af- 

 ter the species of the felspar genus, on account of its 

 tunposed affinity with them ; bat its characters are 

 itill so imperfectly known, that it cannot be arranged 

 in any of the present genera. 



' SODALITC, Jameson. Sodalite, Thomson, 



Internal Character*. Colour intermediate between 

 celandine and mountain-green. Occurs massive, and 

 crystallized in rhomboidal or garnet dodecahedrons. 

 Externally smooth, shining, or glistening ; internally 

 longitudinal fracture vitreous, cross fracture resinous. 

 Has a double cleavage. Fracture conchoidal. Frag- 

 ments indeterminate angular, and sharp-edged. Trans- 

 lucent. Hard as felspar. Brittle; easily frangible. 

 Specific gravity = 2.978. 



Chemical Character*. When heated to redness, it 

 does not decrepitate, nor fall to powder, but becomes 

 dark-grey ; and is infusible before the blowpipe. 



ite. 



Contt. Part* Silica, . . 38.52 Oryctogno- 



Alumina, . 27.58 

 Lime, . . 2.70 ~~*~~ 



Oxide of Iron, 1.00 



Soda, . 25.50 



Muriatic Acid, . 5.00 

 Volatile Matter, 2.10 



Loss, . . 1.70100.00 



Thornton, in Tr. R. S. of Ed. vol. vi. p. 394. 

 Geognoslic and Geographic Situations. It was dis- 

 covered at Kanerdluarsuk, a narrow tongue of land, 

 upwards of three miles in length, in lat 01, in West 

 Greenland, by Sir Charles Giesecke. It is found in a 

 bed from six to twelve feet thick, in mica-slate, and is 

 associated with sahlite, augite, hornblende, and garnet. 

 CLAY and LITHOMAHOB FAMILIES. The minerals 

 included under these titles have no regular form or 

 cleavage, and cannot therefore be connected with any 

 of the mineral species. We place them here on ac- 

 count of their affinity with some of the members of the 

 preceding genus. 

 CLAY FAMILY. 



In this group or family we include the following mi- 

 nerals, 1. Alumhiite, 2. Common Clay, 3. Variegated 

 Clay, 4. Slate-Clay, 5. Bituminous Shale, 6. Clay- 

 stone, 7. Adhesive Slate, 8. Polier Slate, f). Tripoli. 



** LlTHOMARGE FAMILY. 



The minerals of this family have many alliances with 

 the preceding, and hence are placed immediately after 

 them. 



1 . Lithomarge, 2. Mountain Soap, 3. Yellow Earth, 

 4. Bole. 



CLAY FAMILY. c ,, y Fanii . 



1. ALOMINITE, Jameson. Reinc Thonerde, Werner, ly. 



External Character*. Colour snow-white, which 

 verges on yellowish-white. Occurs in small reniform 

 pieces. DulL Fracture fine earthy; consistence in- 

 termediate between friable and solid. Opaque. Soils 

 slightly. Affords a glistening streak. Adheres feebly 

 to the tongue. Passes from very soft into friable. 

 Feels fine, but meagre. 



Conitituent Part*. -Alumina. . 51.0 



Water, . . 45.0 

 Sulphuric Acid, 81.5 

 Lime, . 2.0 99.5 



Buchoiz. 



(ifvgnnstic and Geographic Situation. It occurs in 

 calcareous loam in the alluvi.il strata around Halle in 

 Saxony. 



9. COMMON CLAY, Jameson. 



L'nder this head we include Loam and Potter's-Clay. 



LOAM, Jameson. Leim, Werner. Loam. 



External diameters. Colour yellowish-grey, some- 

 times inclining to greenish-grey, and is spotted yellow 

 and brown. Occurs massive. Dull, and feebly glim- 

 mering, when small scales of mica are present. Frac- 

 ture coarse and small-grained uneven in the large, and 

 in the small earthy. Soils slightly. Very easily fran- 

 gible. Sectile, and the streak slightly resinous. In- 

 termediate between friable and soft, but inclining more 

 to the first. Adheres slightly to the tongue. Feels ra- 

 ther rough, and very slightly greasy, or meagre. 



Geognoslic and Geographic Situations. It occurs in 

 great beds in alluvial districts. 



I 'set The mud-houses we meet with in different 

 countries are built of loam. The use of loam-bricks is 

 of high antiquity ; for we are told that the ancient city 

 of Damascus, and the walls of Babylon, were built oi 

 bricks of this substance. 



