PLATE XL 
Figs. 1 and 2.—Fluor-Spar. 
1. Fluor-Spar , violet, perfectly transparent; two large cubes united as twins. On the upper surface the planes of 
single small cubes are visible. From Cumberland. 
2. Fluor-Spar , in attached crystals, striated violet and white. On the upper surface separate cubic planes are seen. 
Also from Cumberland. Is manufactured in England into cups, and all kinds of small objects of art. 
Figs. 3— 6. — Baryta Compounds. 
3. Witherite , carbonate of baryta, double hexagonal pyramid, originating from the right rhombic prism by double 
truncation of the basal edges and of the acute basal angles. 
4. Barytes , sulphate of baryta, primary form, a right rhombic prism, tabular. From Hungary. 
5. The same , with truncation of all the basal edges. From the veins of variegated sandstone of the Schwarzwald. 
6. The same , a horizontal prism, with truncation of the obtuse angles, to the extent of causing the terminal planes to 
disappear. From Auvergne. 
Figs. 7—9.—Strontia. 
7. Cdestine , Sulphate of Strontia , a horizontal prism. The right rhombic prism is so truncated at the obtuse angles 
that the terminal planes are still visible. From Grirgenti, Sicily. 
8. The same , with truncation of the acute and of the obtuse angles. Also from Grirgenti. 
9. The same , aggregated in a druse on native sulphur. The crystals are obliquely upright; the obtuse angles are simply, 
and the acute ones doubly, truncated. From the same locality. 
Figs. 10—13.—Salts of Potash. 
10. Sulphate of Potash, a rhombic prism, converted by truncation of the basal edges and of the acute angles, into an 
hexagonal double pyramid ; the product of manufacture. 
11. Potash Alum , or sulphate of alumina and potash, a regular octahedron ; five crystals like a staircase above one 
another ; a product of manufacture. 
12. Saltpetre , nitrate of potash, right rhombic prism, with truncation of the obtuse lateral edges, double truncation of 
the obtuse angles and simple truncation of the basal edges. 
13. The same , rhombic prism with truncation of the obtuse lateral edges, of the obtuse angles, and of the basal edges ; 
combination of the hexagonal prism with the hexagonal double pyramid of the rhombic system. 
Figs. 14—17.—Salts of Soda. 
14. Trona , native sesquicarbonate of soda, with four equivalents of water; an oblique rhombic prism, with truncation 
of the obtuse basal angles, from Merida in Columbia. 
15. Soda, simple carbonate of soda, with ten equivalents of water, an oblique rhombic prism, with truncation of the 
basal edges (oblique rhombic octahedron), an artificial crystal. 
16. Fibrous Rock-Salt, coloured red by oxide of iron, from the lower surface of the rock-salt in the shell-limestone 
•at Wilhelmsgliick, in Swabia. 
17. Nitrate of Soda, obtained by crystallization from the Chili saltpetre rhombic hexagon, with ladder-like arrangement 
of the crystalline planes aggregated in a druse. 
Figs. 18 and 19. —Borate of Magnesia. 
18. Boracite. The primary form is a tetrahedron, plainly marked at the alternate angles of the cube by hexagonal 
planes, the edges of the cube truncated (a combination of the tetrahedron with the cube and rhombic), from the gypsum of 
Liineburg. 
19. Boracite, tetrahedron, cube and pyramidal tetrahedron, from the same locality. 
Figs. 20—25.— Salts of Soda — continuation. 
20. Rock-Salt, chloride of sodium, primary form, a cube with truncated angles, from Salzburg. 
21. Kitchen or Table Salt , as it is separated by evaporation of brine in the salt-pans, scalariform arrangement of the 
segments of the cube, hollowed out like a funnel in the middle. 
22. Tincal , native borate of soda, primary form an oblique rhombic prism, with truncation of the obtuse lateral edges 
and of the acute basal edges. 
23. Glauberite , native sulphate of soda, primary form an oblique rhombic prism, with truncation of the basal edges, 
angles, and lateral edges. 
24. Epsomite, sulphate of magnesia with seven equivalents of water, right rhombic prism, primary form, with truncation 
of the basal edges (rhombic octahedron) and of two vertical and lateral edges ; artificial product. 
25. Sal-Ammoniac, chloride of ammonium, cube, twins, both crystals so united that the edges of the cube diverge in a 
radiated manner: extracted from an animal oil in the manufacture of rough sal-ammoniac. 
