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 77
;Wl ^: Mjz VV \.t- VjVpN ( / \k V \/ Fiff. 92. very obtuse angles formed by the faces of OP, or P and P(as well as those of Poo, or x and a?), are a very charac-teristic appearance; marking out this mineral at once as atriclinohedric species. Usually the twin formation is re-peated, three or more… … 10 A POPULAE TREATISE ON GEMS. observed in triclinoliedric felspars, particularly the albiteand labradorite, is that the twin axis corresponds with thatnormal of the -brachydiagonal which issituated in the plane of the base. Inpericline, a variety of albite, these twinsappear as in fig. 93, where…
Precious stones · Building stones · Mineralogy
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