Elements of mineralogy, crystallography and blowpipe analysis from a practical standpoint .. . Fig. 188. Fig. 189. Fig. 190. The value of mc may be determined by the equation, Fig. 189, tan i ^ = —•^ a 6. Prism. Composed of four faces. Fig. 190, each parallel to the verticalaxis and cutting the basal axes in distances not simply proportionate. The intercepts on the basal axes may be in the unit ratio or oneof the intercepts may be relatively lengthened. The types receive names and symbols as follows : Unit Prism, d? c^c I Macro Prism, a : ?ib : ixi c i - n <J hl:o \- Brachy Prism,
Elements of mineralogy, crystallography and blowpipe analysis from a practical standpoint .. . Fig. 188. Fig. 189. Fig. 190. The value of mc may be determined by the equation, Fig. 189, tan i ^ = —•^ a 6. Prism. Composed of four faces. Fig. 190, each parallel to the verticalaxis and cutting the basal axes in distances not simply proportionate. The intercepts on the basal axes may be in the unit ratio or oneof the intercepts may be relatively lengthened. The types receive names and symbols as follows : Unit Prism, d? c^c I Macro Prism, a : ?ib : ixi c i - n <J hl:o \- Brachy Prism, . — n ^ kho \ The value of na can be determined by the equation. Fig. 190. cot i X= na. S: 672 YSTALLOGRAPHY. Combinations in the Pyramidal Class. Barite.—Axes a : ^ : c = : i: The prevailing faces are the unit prism m, the basal pinacoid c,the macro dome n= (a: 00 b: i c), and the brachy dome, d =( oo« ). Fig. 191. Fig. 192. Fig. All of these are shown in Fig. 196. Fig. 195 contains also thebrachy pinacoid h and Fig. 193 the macro pinacoid a. Figs. 191,192 and 194 are simpler combinations of the same forms. Topaz.—Axes d: ~b : c = : i : Fig 197 shows the unit pyramid /, unit prism in, brachyprism / = (2« ? 00 c) and the brachy dome / =( 00 a : b : 2c).Fig. 198 shows the same forms with the basal pinacoid c and Fig. 197. Fig. ic Fig. 199.
Size: 2476px × 1009px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookpublishernewyorkdvannostran
