A popular treatise on gems, in reference to their scientific value; a guide for the teacher of natural sciences, the jeweller, and amateur: together with a description of the elements of mineralogy, and all ornamental and architectural materials .. (1859)
Feuchtwanger, Lewis. [from old catalog] · New York, D. Appleton & company · leaf 53
ht angles toeach other. One of these is assumed as the chief axis,when the others are named subordinate. The plane pass-ing through the secondary axes, or the basis, forms arhomb, and from this the name is derived. This systemcomprises only a few varieties of forms that are essentiallydistinct, and… … Fig. 49. lateral edges lie in one plane, and form a rhomb. They have eight polar edges,—four acute and four more obtuse, —and four lateral edges, and six rhombic angles, the most •acute at the extremities of the longest axis. {2d.) The rhombic sphenoids (fig. 49) are bounded by four scalene…
Precious stones · Building stones · Mineralogy
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