WARREN AND PALACHE. — QUIXCT PEGMATITES. 13') 



minute black inclusions and fluid cavities often with moveable bubbles. 

 The extinction of the (juartz is usually (juite uniform, there being little 

 indication here of strains or crushing. The riebeckite forms rather 

 flat, elongated prisms (1 to 5 mm. broad by 10 to o(» mm. long), but 

 without terminations, the ends being always frayed or continued with 

 aegirite. Aegirite with the exception of the growths on the riebeckite 

 and the microlites in the feldspars is rather sparingly present in this 

 graphic-granite zone. 



The zone just described passes almost imperceptibly into the next 

 and principal zone (C in Figure 1) whose leading characteristic is per- 

 haps its irregularity of grain. Running through this material in a direc- 

 tion parallel to the outer margin is a narrow strip of graphic-granite 

 (crossed in figure). It consists essentially of greenish-white crystals 

 of albite-microcline-microperthite ; irregular grains of semi-transparent, 

 grayish quartz, long black riebeckite prisms, often much intergrown 

 and practically always surrounded and terminated on the ends by 

 aegirite ; aegirite prisms and grains ; filling in the spaces between the 

 larger grains is a considerable amount of fine-grained material. This 

 may be light green in color when aegirite is abundant, but more com- 

 monly is brownish or brownish red. Occasional small crystal pockets 

 occur in this zone, and in these parisite, fluorite, ilmenite, and second- 

 ary riebeckite have been noted. Parisite grains have also been found 

 closely associated with aegirite and quartz, particularly near the quartz 

 center. The fine material forms a more or less continuous network 

 through the zone and in places forms patches of a centimeter or more 

 across. Toward the central quartz zone the fine material seems to in- 

 crease in amount and immediately about the quartz it constitutes 

 almost a distinct zone itself. 



Under the micro.scope the fine material is seen to consist of variable 

 amounts of quartz, microcline with a little microperthite and albite, 

 aegirite, zircon and ilmenite, magnetite (?), calcite and certain poorly 

 defined decomposition products. The quartz and feldspar occupy 

 spaces of about equal size, but under crossed nicols the feldspar breaks 

 up into a mosaic of small equi-dimensional grains. The quartz shows 

 an undulatory extinction. The aegirite is abundant in the shajie of 

 irregular grains lying fur the most part in the (juartz areas or between 

 the (juartz grains and the microcline. Many of the smaller grains lie 

 grouped in such a manner as to suggest that they were once ])art8 of a 

 single crystal. Zircon is very abundant, particularly in quartz-rich 

 portions of the fine material, and while some of the grains will meas- 

 ure 1 to 2 or perhaps 3 mm. on a side and exhibit well-developed 

 short prisms capped by unit pyramid.s, the majority are small and ap- 



