534 



MINERALOGY. 



Oryctogno- The chemical characters and composition of this sub- 



>' stance have not been ascertained. 



~" Y " Geognostic and Geographic Situations. It occurs in 



granite and gneiss districts, as in Cairngorm and Arran 

 in Scotland, and Cornwall in England. It is well 

 known in Saxony, and other countries. 



NINTH SUBSPECIES. 



Porcelain PORCELAIN EARTH, or KAOLIN, Jameson. Porcella- 

 earth. nerde, Werner. 



External Characters. Most frequent colour reddish 

 white, of various degrees of intensity ; also snow-white 

 and yellowish- white. Generally friable, and sometimes 

 approaches to compact. Composed of dull dusty par- 

 ticles, which are feebly cohering. Soils strongly. Feels 

 fine and soft, but meagre. Adheres slightly to the 

 tongue. Specific gravity, 2.216, Karsten. 



Chemical Characters. It is infusible before the 



blowpipe. 



Silica 

 Alumina 



Oxide of iron 0.25 

 Water 14.50 



97.75 



Constituent Parts. 

 Porcelain Earth from 



Auein Saxony. 

 46.0 Silica 52.00 

 39.0 Alumina 47-00 

 Iron 0.33 



99.33 

 Rose. 



Silica 55.0 

 Alumina 42.5 

 Iron 1.0 



Lime 1.0 



99-5 

 Gehlen. 



Pyramidal 

 Felspar. 



Radiated 

 Scapolite. 



.K/a/5nrtA,Chem.Abhandl. s. 278. 



Geognosiic Situation. It generally occurs in granite 

 and gneiss countries, either in beds contained in the 

 granite or gneiss, when it appears to be an original de- 

 posite, or on the sides and bottom of granite and gneiss 

 hills, when it is certainly formed by the decomposition 

 of the felspar of these rocks. 



Geographic Situation. It occurs in different gra- 

 nite and gneiss districts in Scotland, and in the Shet- 

 land Isles ; also in England and Ireland, and in many 

 places on the continent of Europe. 



Uses. This mineral forms a principal ingredient in 

 the different kinds of porcelain. It is not used in the 

 state in which it is found in the earth, but is previous- 

 ly repeatedly washed, in order to free it from impuri- 

 ties. After the process of washing, only fifteen parts 

 of pure white clay remain, which is the kaolin of the 

 Chinese. Porcelain has been manufactured in China 

 and Japan from a very early period. The art itself 

 was discovered in Europe by a German named Botti- 

 cher, who made his first porcelain- vessels in Dresden in 

 the year 1706. These were of a brown and red colour. 

 The white was not attempted until the year 1709 ; and 

 the famous manufactory at Meissen, the earliest in Eu- 

 rope, was established in 1710. 



4. PYRAMIDAL FELSPAR, or SCAPOLITE t, Jameson. 

 Pyramidaler Feldspath, Mo/is. Scapolit, Werner. Pa- 

 ranthine, Hauy. 



Pyramid = 136 28' 62 56'. Cleavage is in the 

 direction of the lateral planes, and of the diagonals of a 

 rectangular four-sided prism. Hardness = 5.0 5.5. 

 Sp. gr. = 2.52.8. 



This species is divided into four subspecies, viz. Ra- 

 diated Scapolite, Foliated Scapolite, Compact Red Sca- 

 polite, and Elaolite. 



FIRST SUBSPECIES. 

 RADIATED SCAPOLITE, Jameson. 

 External Characters. Most frequent colour grey, 

 seldomer white and green. Occurs massive, and in 

 distinct concretions ; concretions radiated or fibrous, 

 scopiform diverging, and are collected into others which 

 are thick and wedge-shaped. It is most frequently 

 crystallized. The secondary forms are the following : 



I . Rectangular four-sided prism, flatly acuminated Oryctogno. 

 on the extremities with four planes, which are set on y- 

 the lateral planes. 2. The preceding figure, in which V ""~V^ P ' 

 the lateral edges are truncated. 



Lateral planes of the crystals deeply longitudinally 

 streaked, and shining. Internally intermediate between 

 shining and glistening, and the lustre intermediate be- 

 tween resinous and pearly. Fracture fine-grained 

 uneven. Translucent, and semitransparent in crystals. 

 Chemical Characters. Green scapolite, before the 

 blowpipe, becomes white, and melts into a white glass. 

 Constituent Paris. Silica, . 45.0 



Alumina, , 33.0 

 Lime, . 17.6 



Natron, . 1.5 



Potash, . . 0.5 

 Iron and Manganese, 1.098-6 

 Laugier, Annales du Museum d'Hist. 



Nat. cah. Ix. p. 472. 



Geognostic and Geographic Situations. This mine- 

 ral occurs in the neighbourhood of Arendal in Norway, 

 where it is associated with magnetic ironstone, felspar, 

 quartz, mica, garnet, augite, hornblende, actynolite, 

 and calcareous-spar. 



SECOND SUBSPECIES. 



FOLIATED SCAPOLITE, Jameson. Foliated 



External Characters. Principal colours grey, green, Scapolite. 

 and black. Occurs massive, disseminated, and in large, 

 coarse, and long angulo-granular concretions; also 

 crystallized in low eight-sided prisms, flatly acuminat- 

 ed with four planes, which are set on the alternate la- 

 teral planes. Externally crystals shining or splendent, 

 and vitreous. Cleavage shining, fracture glistening ; 

 lustre intermediate between resinous and pearly. Ge. 

 nerally translucent, and passes sometimes into transpa- 

 rent, sometimes to translucent on the edges. Yields a 

 white streak. 



Geognostic and Geographic Situations. It occurs 

 in Sweden, in primitive rocks. 



THIRD SUBSPECIES. 

 COMPACT RED SCAPOLITE, Jameson. Dichter Scapolite. Compact 



External Characters. Colour dark brick-red, pass- red Scapo- 

 ing into pale blood-red. Seldom occurs massive, more lite - 

 frequently crystallized, in long, frequently acicular, 

 four-sided prisms, which are often curved, and are with- 

 out terminal crystallizations. Externally crystals rough 

 and dull. Internally very feebly glistening, almost 

 glimmering. Fracture fine-grained uneven, approach- 

 ing to splintery. Opaque, or very faintly translucent 

 on the edges. 



Geognostic and Geographic Situations. It occurs 

 along with the other subspecies, in metalliferous beds 

 at Arendal in Norway. 



FOURTH SUBSPECIES. 



ELAOLITE, Jameson. Elaolith, Klaproth. Fettstein, Elaolite. 

 Werner. Dichter Wernerit, Hausmann. 



External Characters. Colours of this mineral blue, 

 which inclines more or less to green, also flesh-red, 

 which falls more or less into grey, sometimes even in- 

 clines to brown. Occurs massive, and in very inti- 

 mately aggregated granular concretions. Internally 

 shining or glistening, lustre resinous. Fracture princi- 

 pally in the red variety, flat and imperfect conchoidal. 

 Blue variety has an imperfect double cleavage. Trans, 

 lucent in a low degree. Blue variety, when cut in a 

 particular direction, displays a peculiar opalescence, 

 not unlike that observed in the cat's-eye. Has the 

 same degree of hardness as the other subspecies. 



Chemical Character. When pounded, and thrown 







