PLATE XVIII. 
Fig. 1.—Magnetic Pyrites. 
1. Magnetic Pyrites, hexagonal prism, with transverse striation, from Kongsberg in Norway. 
Figs. 2—8.—Pyrites. 
2. Pyrites , twelve-faced pentagon, the usnal form, from Traversella in Piedmont. 
3. The same , cube and twelve-faced pentagon, from Herrensegen in the Schwarzwald. 
4. The same , trapezoidal twenty-four-faced figure, from Traversella. 
5. The same , regular octahedron, with drusy faces, from the Harz. 
6. The same , arborescent aggregation of octahedrons, from Schneeberg. 
7. The same , groups of cubes, with the peculiar striations in each of the two directions of the parallel edges, from 
Tavistock. 
8. Pyrites , as the petrifying medium of an ammonite (yl. Amaltheus ), and a group of small crystals attached, cubes with 
truncation of the angles, from the lias schist at Boll. 
Figs. 9—12.—Spear Pyrites. 
9. A group of crystals of the spear pyrites , or prismatic iron pyrites , from Saxony. 
10. Spear Pyrites , rhombic prism, the primary form, with truncation of the acute angles. 
11. The same , united as twins, and stellate. 
12. The same , rhombic octahedron, with truncation of the basal angles and terminal edges of Fig. 10. 
Figs. 13—16.—Magnetic Iron. 
13. Magnetic Iron , twins of two half octahedrons, from Pfitsch in the Tyrol. 
14. The same , octahedral table, half octahedron, from the same locality. 
lo. The same , octahedron, with truncation of the angles (cube) and of the edges (rhombic dodecahedron), from 
Piedmont. 
16. Magnetic Iron , crystallised in rhombic dodecahedrons, small group of crystals, from Traversella in Piedmont. 
Figs. 17—21.—Iron-Glance, Red Oxide of Iron, Haematite. 
17. Iron-Glance in the primary form, a rhombohedron, with truncation of the vertex, from Vesuvius. 
18. The same , a rhombohedron, in combination with four other derived rhombohedrons, from the island of Elba. 
19. The same , an hexagonal double pyramid in a tabular form, from St. Gothard. 
20. The same , an hexagonal prism, the so-called iron rose , from St. Gothard. 
21. Fibrous Red-iron or haematite , from Schwarzenberg in Saxony. 
Figs. 22 and 23.—Brown Iron Ores. 
22. Needle Iron Ore or Gothite, in right rhombic prisms, with truncation of the angles and basal edges, from Cornwall. 
23. Fibrous Limonite, of a yellowish-brown colour, stellate and compact, from Thuringia. 
