WARREX AND PALACHE. — QUIXCY PEGMATITES. 127 



For a rock so high in silica the iron is notably high ; the alkalies are 

 also high, particularly the soda, and account for the abundant soda- 

 iron amphibole and pyroxene present in the rock. MgO and CaO are 

 very low. At least one third of the lime is present as calcite. 



Occurrences of Pegmatite in the Quincy-Blue Hill Area. 



Up to the present time the following pegmatites have been noted in 

 the area : 1st. Crossing the top of Rattlesnake Hill (eas^cent^al part 

 of the area) in a nearly E. W. direction, is a narrow, dike-like vein of 

 pegmatite. It has been traced for about 60 feet and varies from H to 

 10 inches in width. Structurally it is somewhat similar to the pegmatite 

 pijies to be described beyond, having on both margins a zone of fine 

 graphic-granite succeeded toward the center by rather coarse feldspar 

 and quartz containing riebeckite. The center contains a few small 

 crystal pockets and occasional masses of quartz. Another smaller and 

 less regular vein of similar character occurs nearby. 



2nd. On the low hill lying south of North Common Hill, Quincy, and 

 just east of the railroad near Pine Hill on the top near its southern 

 brow, are several veins and irregular spots of pegmatitic character. 

 The granite near the top and on the steep southern slope of the hill 

 is capped by a fine-grained granitic rock with a strong tendency toward 

 a porphyritic texture. It dips gently to the south. It is in sharp 

 contact with the granite and along the contact is frequently a rather 

 abundant and coarse-grained development of riebeckite crystals. A 

 few feet north, and underneath the contact in the granite, is an irregular 

 streak of fine-grained granitic rock which contains streaks of much 

 coarser quartz, feldspar, and riebeckite. Its width will average in the 

 neighborhood of two feet and its length, while considerable, cannot be 

 closely determined. While this may be a dike it may also be a detached 

 piece of the overlying fine-grained rock. Its exact nature has not yet 

 been determined. The granite in several places near the contact shows 

 a local coarsening of the grain forming pegmatitic spots made conspic- 

 uous by presence of long black riebeckite crystals. Several vein or 

 dike-like streaks of coarse texture also intersect the granite here. The 

 smaller ones vary from one to about four inches in thickness, and are 

 more or less irregular in course, and of only a few feet or yards in 

 length. They consist essentially of feldspar, the usual microcline- 

 microperthite albite, riebeckite, and (juartz, and are for the most part 

 considerably coarser in grain than the granite, but also contain a vari- 

 able amount of fine granitic material. This sometimes forms a streak 

 along the margin and again has an irregular distribution through the 



