Plate 23
Crystals of green corundum in syenite, from Montana
Typical crystal forms of corundum: A the elongated prism with the alternate corners cut by rhombohedral faces, B the tabular prism, C the double pyramid
Plate 28
Cassiterite, twinned crystals
The crystal form in which both cassiterite and rutile occur when in simple crystals, p prism faces, m beveling of the prism, o octahedral face, n beveling of the edge between octahedral faces