CHABAZITE 471 



the faces and slight distortion it fairly well represents an actual crystal, 

 although the crystal as it occurs does not show all the faces represented 

 in the drawing. It is very common to find one of the interpenetrating 

 crystals smaller than the other, as is shown in figure 2 of plate 49, but 

 other crystals show every possible degree of distortion of one or both of 

 the two individuals. In many cases one of the interpenetrating indi- 

 viduals may be almost suppressed or, what amounts to the same thing, 

 may show just a corner of the rhombohedron projecting from the face of 

 the other and larger individual ; but, with all the varying degrees of dis- 

 tortion and suppression, three of the forms are almost always to be seen. 

 These are R, — 2 R, and oo P2 — that is, R, s, and a. The flatter rhombo- 

 hedron e is very often missing, or is present on one and missing on the 

 other twinned individual. 



The two scalenohedrons are never present as distinct faces, but as 

 strongly developed striations. Nevertheless they are well enough devel- 

 oped to give distinct flashes of light. By their intersections they form 

 flat ridges upon the faces of the rhombohedron R. Almost always one 

 of these striating scalenohedrons may be detected, while the other one 

 is mainly absent. 



The more common of the two scalenohedrons striates R parallel to the 

 rhombohedron edges that meet at the vertex of the crystal — that is, 

 parallel to the edge formed by R and e. It forms by the intersections of 

 the striations a very flat ridge on the face of R, running from the top of 

 the crystal down toward the middle of the face. The other scaleno- 

 hedron striates R on the lower part of the face parallel to the zigzag 

 edges — that is, parallel to the edge formed by R and a. It forms a flat 

 ridge that runs from the point of intersection of two lateral edges up- 

 ward till it meets the ridge formed by the other scalenohedron. By 

 their mutual intersections these two scalenohedrons also form two hori- 

 zontal flat ridges. Thus four ridges are formed that divide the face R 

 into quadrants. The above description of the striating scalenohedrons 

 applies, of course, only to ideally or symmetrically developed crystals, 

 such as are never realized in nature. As a matter of fact, only occa- 

 sionally do the striations approach to symmetry. In nearly all cases 

 the flat striation ridges are shoved to one side or the other or are entirely 

 crowded off. An attempt to illustrate this distortion of the scalenohedral 

 striations is made in the shading of the faces of R in figure 2 of plate 49. 



As far as is known to the writer, the chabazite crystals that are most 

 nearly akin to these from Golden are the crystals from the phonolite 

 near Rubendorfel, in Bohemia* These crystals from Riibendorfel (com- 



* Doctor C. Hintze : Handbuch der frjineralogie, Leipzig, 1897, p. 1777, 



