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 40
Fig. 20. Fig. 21. common predominant forms. In fig. 20 two tetrahedrons in opposite positions, — .•——, are combined. In fig. 21 a 2* 34 A PRACTICAL TREATISE ON GEMS. very comi^lex combination of seven forms is represented ina crystal of gray-copper ore, its full sign being— If {I) . coOoo (/) .…
Precious stones · Building stones · Mineralogy
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