WARREX AND PAL.\CHE. — QUINCT PEGMATITES. 137 



section made up of the forms 110 and 010. Terminal planes are 

 wliolly wanting. Without exception the riebeckite is intergrown with 

 aegirite. Commonly in parallel position, though again without definite 

 orientation (c axis in common), the aegirite may occur (^uite at ran- 

 dom in the body of the riebeckite, but it is most abundant about the 

 outside, particularly on the ends, forming an almost or quite continu- 

 ous shell about the riebeckite. Indeed the ends of the riebeckite crys- 

 tals are usually continued as a solid mass of aegirite. The aegirite 

 may almost wholly replace the other mineral, there being only a core 

 or a few shreds of riebeckite visible. Besides this mode of occurrence 

 the aegirite is found scattered throughout the coarser parts of the rock 

 and as noted, abundantly in the finer material — and as inclusions in 

 the feldspar. The habit of the aegirite is distinctly toward a delicate 

 columnar structure parallel to the vertical axis, and when broken the 

 fracture is usually splintery. Often there is a marked radial arrange- 

 ment of the prisms or groups of prisms. This habit is especially com- 

 mon along the contact with the quartz center where clusters of some 

 size occur, the tapering aegirites extending out into the quartz. Occa- 

 sional separate crystals may be seen lying in the massive quartz 3 or 

 4 mm. in thickness and several centimeters long. In general through- 

 out this zone the main part of the aegirite, although clearly more 

 closely connected with the quartz in period of formation than with 

 any other mineral, appears to have to some extent preceded it, since a 

 tendency toward automorphic outlines is commonly observed with 

 reference to the quartz. Its color is prevailingly grass-green. 



A commonly noted feature of the aegirite-riebeckite crystals is the 

 occurrence in their midst of spots consisting of dark purple tiuorite 

 grains, associated with ilmenite, zircon, calcite. These are often stained 

 with ferruginous products. 



The central (quartz (D of figure) is massive in character, semi-trans- 

 lucent and of a grayish or grayish-white color. Like the rest of the 

 quartz it contains minute inclusions and cavities often with bubbles- 

 Masses of granular galena and sphalerite, one nearly as large as a man's 

 fist, also similar sized pieces of a very dark purple fiuorite occur in 

 places through the center of the quartz. Some of these were associated 

 with blue crocidolite like that found in the large pockets. 



On the other and western side of the pipe, the succession of zones is 

 essentially the same except that they are not quite so wide. 



Through the lower and thicker i)art of the pegmatite containing the 

 large central pocket the section differs somewhat from that given above, 

 is less regular, and shows sudden changes in character difiicult to de- 

 scribe. Going from east to west through its thickest jwirt we meet 



