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NEW YORK STATE MUSEUM 



Rhombohedron. The rhombohedron (fig. 106, 107, model 8) i& 

 composed of six rhombic faces, each of which intersects two 

 basal axes at equal distances, is parallel 

 to the third and cuts the vertical axis (c). 

 The two rhombohedrons possible for every 

 relative value of the vertical intercept are 

 complementary plus (fig. 106) and minus 

 (fig. 107); the 12 faces of the plus and 

 minus rhombohedrons include all the 

 faces of a hexagonal pyramid of the first 

 order having the same relative intercepts. Some rhombohe- 

 drons of calcite of varying vertical intercepts are shown in fig. 

 107-9. 



Fig. 106 F ig. 107 



Fig. 108 Fig. 109 



Scalenohedron. The scalenohedron (fig. 110) is composed of 12 

 scalene triangular faces each of which cuts all four axes. As 

 with the rhombohedron two forms are possible for every value 

 of the vertical intercept. These are related to the dihexagonal 

 pyramid in the same way that the rhombohedron is related to 

 the pyramid of the first order. 



