PLATE X. 
Figs. 1—3.—Areagonite, 
1. Crystal of Arrayonite, double twins, a right rhombic prism, with truncation of the acute lateral edges and of the 
acute angles, yellowish-white, transparent, from Waltsch, in Bohemia. 
2. Reddish Arragonite, rhombic prism, with truncation of the acute lateral edges, from Molina in Arragon. These 
crystals are composed of numerous smaller ones, so arranged, however, that individual planes appear to be lustrous. 
3. Crystallised Arrag onite , a druse of rhombic pyramids, acicular and spear-like, from Leogang in Salzburg. 
Figs. 4—6.—Brown Spar, Bitter Spar, Carbonate of Lime, with Protoxide of Iron and Manganese. 
4. Reddish-brown spar , the so-called ankerite, from the lodes of micaceous schist at Schneeberg in the Erzgebirge. 
5. Compact-brown spar , striped with white, yellow, and green, so-called agate marble from Algiers, frequently cut and 
used as marble in Paris. 
6. The same , with brown undulations, from Gibraltar. 
Figs. 7—10.—Gypsum, Hydrous Sulphate of Lime. 
7. Gypsum,, primary form an oblique rectangular prism. 
8. The, same , with truncation of all the basal edges, an oblique rectangular octahedron, from Derbyshire. 
9. The same, two crystals aggregated as twins, from Bex in Switzerland. 
10. Splinter of a lenticular twin , yellowish-white, from the gypsum quarries of Paris. 
Figs. 11 and 12.—Anhydrite, Anhydrous Sulphate of Lime. 
11. Anhydrite , a right rectangular prism, with truncation of the right angles, from Salzburg. 
12. Reddish Anhydrite , primary form, a right rectangular prism ; the cleavage in three different directions is indicated on 
the lateral planes, from Hallein in Salzburg. 
Figs. 13 and 14.—Apatite, Phosphate of Lime. 
13. Apatite , primary form, a regular hexagonal prism, from Schlackenwald in Bohemia. 
14. The same, green, the hexagonal prism in combination with truncation of all the basal edges (first hexagonal double 
pyramid), and of all the angles (second acute hexagonal double pyramid), from the same locality ; still more composite crystals, 
with double and triple truncation, are found at St. Gotbard and in the Tyrol. 
Figs. 15—18.~Fi.uor Spar, Fluoride of Calcium, or Fluate of Lime. 
15. Fluor spar , a regular octahedron, bounded by eight equal-sided triangles, the primary form. Is found rose-red at 
St.. Gotbard, in the Canariathal, and in Hnterwalden ; green at Breitenbronn in Saxony. 
16. Fluor spar, yellow, cube with truncated angles, from Saxony. 
17. The same , dichromate, by reflected light blue, and by transmitted light emerald-green ; twins, a cube with doubly 
truncated edges (pyramidal cube), half the natural size, from Derbyshire. 
18. The. same , cube with triple pointing of angles (48-sided figure), from the MLiusterthal, near Freiburg in Breisgau. 
