CRYSTALLOGRAPHY. 



475 



Meionite. 



tals of pyrites from each other • and Hauy has lately 

 cortstituted two species. The first, called sitlphuret of 

 iron, has a cube for its primitive form. The second, 

 called wh 'le sulphttret of iron, has a rhomboidal prism 

 for its primitive form, and includes under it all the oc- 

 tahedral crystals of pyrites. If reliance can be put up- 

 on the analysis of Hatohett, the composition of these 

 two sulphurets is the same. They therefore constitute 

 an anomaly in the theory of crystallization, similar to 

 that already known in the difference between arrago- 

 nite and calcareous spar. 



8. Glance cobalt ore. This ore, which occurs in Swe- 

 den, is usually crystallized in cubes, or figures derived 

 from it. 



Q. Phosphate of mangancse-ana-iron, or pitchy iron 

 ore. 

 ( 10, 11, 12. Native gold, silver, and copper. 



II. Right quadrangular Prism, base a Square. 



This primitive form, which may be considered as a 

 lengthened cube, belongs to eight species of minerals, 

 namely, 



1 . Sulphate of magnesia. It crystallizes in rectan- 

 gular prisms, the bases of which are squares. This 

 form is by no means Uncommon, though it is more 

 usual to observe the prism terminated by four-sided py- 

 ramids, as is represented in Fig. 11. 



2. Vesuvian or Idocrase. The primitive form of this 

 substance was at first supposed a cube ; but Hauy af- 

 terwards determined the real form. It occurs usually 

 in six-sided prisms, terminated by five-sided figures, as 

 represented in Fig. 1 2. The narrow vertical faces d, 

 are produced by a decrement of one range on the ver 

 tical edges of the nucleus ; the 4 six-sided terminal 

 faces c, c, c, by a decrement of two ranges on the an- 

 gles of the base. The small face P is the remains of 

 the base. 



3. Meionite. This mineral, like the last, occurs in 

 the lava of Mount Vesuvius. The crystals are very 

 small, and are usually eight or twelve sided prisms. 

 The most common variety is represented in Fig. 1 3. 



4. Mcsotype, or radiated zeolite. This is the mineral 

 originally called zeolite by Cronstedt, a name which 

 ought still to bo preserved The most common varie- 

 ties of its crystals are represented in Fig. 14. and 15. 



5. Parauthine or scapolite, and wernerite. These two 

 minerals seem to belong to the same species. They 

 have been found in Sweden and Norway ; and about 

 five different kinds of crystals have been described. 



6. Chr ornate of lead. It usually occurs in four-sided 

 prisms, terminated by four-sided pyramids. 



7. Uranmica, or green oxide of uranium. 



8. Ruthile, or oxide of titanium. 



III. Right quadrangular Prism, with a rectangular 

 Base. 



This primitive form, like the last, belongs to eight 

 species of minerals. 



1. Cryolite. This triple salt is composed of fluoric 

 acid, soda, and alumina, and has been hitherto ob- 

 served only in Greenland. As far as we know, no re- 

 gular crystals have yet been observed ; but the mineral 

 is foliated, and yields the primitive form by mechani- 

 cal division. 



2. Anhydrous sulphate of lime. The crystals of this 

 curious species hitherto observed, have been described 

 by Bournon in the Jour, de Min. torn. xiii. p. 346. To 

 this description we refer the reader. 



3. Chrysoberyl or cumophane. The most common Crystallinr 

 crystal of this species is represented in Fig. 16". Some Form*. 

 new varieties have been described by Hauy in the An- rfhrv&oht- 

 nales du Mux. d'Hist. Natur. vol. xviii. p. 57. rv i. 



4. Chrysolite or peridot. The most common crystals i- L ate 

 of this species are represented in Fig. 17. and 18. CCXXV. 



5. Stilbife, or foliated zeolite. The crystals of this F'S> 1<i \ 

 mineral are usually long, and very beautiful. Fig 1J) 

 represents the variety that perhaps occurs most fre- stilbite.' 



Chrysolite. 

 Fies.17,18. 



quently 



6. Apophyllite or ichthyophthalmitr. 



F,g. 19. 

 Apophyl- 



The crystals be- 

 longing to this mineral will be found described by l' tf * 

 Hauy in the Jvr. de Min. vol. xxiii. p. 385. One of 

 the crystals described in his mineralogy as belonging 

 to the Stilbite, belongs in fact to this species. 



7. Pre/mile. This mineral, when it is crystallized, Frehnite. 

 usually assumes the figure of a thin rhomboid, similar 



to Fig 20. Fig. 20. 



8. Wolfram. The primitive crystal of this species wolfram.' 

 sometimes occurs ; but a more common variety is re- 

 presented in Fig. 21. The faces marked P, M, T, are Fig- 21- 

 those of the primitive crystal ; the faces s, s, are pro- 

 duced by the decrement A^ 4A. 



IV. Right quadrangular Prism, Base a Rhomb. Right qua- 

 .... . . . drarrtjular 



. This primitive form is equally prolific with any of prism, base 

 the preceding, belonging to no fewer than twelve spe- a rhomb, 

 cies ; namely, 



1. Sulphate of barytes. This species, next to calca- Sulphate of 

 reous spar, is the most prolific in varieties of crystalline barjtes. 

 forms. Hauy has announced, that he intends to de- 

 scribe no fewer than 60 of these in the new edition of 



his Mineralogy. The primitive form occasionally oc- 

 curs in very small crystals, but by far the most common 

 form, at least in this country, is what Hauy calls the 

 trapczicnne, represented in Fig. 22. The symbol for Fig. 22. 



% 1 

 which is A E P, which will be understood from the let- 



doV 

 ters on the figure. 



2. Sulphate of sirontian. A considerable number of Sulphate of 

 varieties of these crystals have been observed, almost all strontian. 

 in Sicily. We have never seen it assume the primitive 



form. A common variety is the unilairc of Hauy, 



a kind of wedge-shaped octahedron, represented in 



1 

 Fig. 23 ; the symbol for which is M E. Fig. 23. 



Mo 



3. Datholfte, or siliceous borate of lime. This scarce Dathotite. 

 species has been hitherto found only at Arendal in Nor- 

 way. The base of its primitive form is a rhomb, with 



angles of 109° 28' and 70° 32' ; and the height of the 

 prism is to a side of the base as l6 to 15. Only one 

 variety of its crystals has hitherto been described, a 

 kind often-sided prism. See Jour, de Mines, vol. 19, 

 p. 362. 



4. Granalile or staurotide. It occurs usually in the Granatite. 

 form of two six-sided prisms crossing each other at Fig. 21. 

 right angles, as represented in Fig 24. 



5. Diaspore. This singular mineral is a compound Diaspore. 

 of alumina and water ; and in this respect agrees with 

 Wavellite. It has not hitherto been found crystallized. 



6. Hyperstene or labradore hornblende. This mine- Hyper- 

 ral has been lately separated from hornblende, and con- stene. 

 stituted a species apart by Hauy. It comes from La- 

 bradore, and, as far as we know, has not hitherto been 

 observed crystallized 



7- Mica. The primitive form of this mineral is a Mien 

 prism, with rhomboidal bases, the angles of which are 

 120° and 60°. It usually occurs crystallized in plates, 



