Plate 20
A characteristic form in which sphalerite may occur; being the combination of, d the dodecahedron, o the octahedron, and t, a 24-sided figure
Characteristic form for zincite crystals, n the hexagonal prism, and p pyramidal faces on it
Typical form of crystal of willemite: p the prism, r rhombohedron faces on end, ½ r a second lower rhombohedron