30 RUBY FAMILY. 13. Thick equiangular six-sided table, in which the terminal planes are set alternately oblique on the lateral planes. Sometimes the table is elongated, when it assumes more the appearance of a 14. Very oblique four-sided table, which is truncated on both the acute angles. 15.. Acute rhomboid, in which the two acute angles are truncated. It is formed by the lessening of two opposite planes of the octahedron. 16. Octahedron, truncated on the edges. Fig 17. 17. Garnet dodecahedron. Fig. 18. 18. Octahedron, in which the axis is oblique, the edge of the common bases is truncated, and the apices sometimes rounded off. 19. Ilefctangular four-sided prism, acuminated by four planes, which are set on the lateral planes Fig. 19, 20. Lengthened or cuneiform octahedron. Fig. 20. All the planes of the crystals that originate from the fundamental figure are smooth; whereas those that are derived from truncations on the edges are streaked. The crystals are generally small and very small; sel dom middle-sized *. Externally and internally the spinel is splendent, and the lustre vitreous. The most frequent fracture is flat conchoidal, some times also concealed foliated ; and the folia are parallel with the sides of the octahedron. T he fragments are angular and sharp-edged, or splin tery. It alternates from translucent to transparent, ami re- fracts single It is hard in a high degree. It scratches quartz very readi.y; but is scratched by sapphire. It * Brard mentions a fine spinel, weighing 215 grains, which was intended for Josephine, the wife of Buonaparte,
