Elements of mineralogy, crystallography and blowpipe analysis from a practical standpoint .. . a:ooc; the face a with interceptsI : 00 : 00 is a: oo«: oor; the face u with intercepts 1:1: isa?y and the face x with intercepts 1:3: is a : 3« : 3c. CLASS OF THE DITETRAGONAL PYRAMID. 15. No. 18. Holohedry, Liebisch. No. 6. Normal, Dana. Symmetry of the Class. As shown in Fig. 83 forms in this class are symmetrical to onehorizontal plane and to four vertical planes at forty-five degreesto each other. The intersections of these planes with each other areaxes of symmetry and of these CC is
Elements of mineralogy, crystallography and blowpipe analysis from a practical standpoint .. . a:ooc; the face a with interceptsI : 00 : 00 is a: oo«: oor; the face u with intercepts 1:1: isa?y and the face x with intercepts 1:3: is a : 3« : 3c. CLASS OF THE DITETRAGONAL PYRAMID. 15. No. 18. Holohedry, Liebisch. No. 6. Normal, Dana. Symmetry of the Class. As shown in Fig. 83 forms in this class are symmetrical to onehorizontal plane and to four vertical planes at forty-five degreesto each other. The intersections of these planes with each other areaxes of symmetry and of these CC is an axis of tetragonal sym-metry. CC and either pair of alternate horizontal axes may bechosen as crystal axes. TETRAGONAL SYSTEM. 25 The General Form or Ditetragonal Pyramid. Weiss, a??mc; Dana, m- n; Miller, { hkl \. Composed of sixteen faces, Fig. 84, each cutting the two basalaxes at unequal but simply proportionate distances, and the ver-tical axis at a distance not simply proportionate to the other dis-tances. In the ideal forms the faces are scalene triangles. Fig. 83. Fig.
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