WARREN AND PAL.\CIIE. — QriNCY PEGMATITES. 141 



figure, that the position of the pocket is not exactly central since 

 the zones on the eastern side are considerably thicker than those on the 

 west which measure each only a few inches. 



The Ctntrnl I'nckit. — The contents of the large central cavity were 

 most unusual in character and consisted essentially of : quartz crystals 

 of all sizes from exceedingly minute individuals up to great crystals, K) 

 cm. thick and 30 cm. long ; rock fragments of all portions of the peg- 

 matite except the dark marginal zone of sizes ranging from that of a 

 walnut up to that of a man's head ; tluorite octahedra, sometimes of 

 large size ; and a thickly felted mass of a delicate, grayish-blue cro- 

 cidolite filled with minute hair-like crystals of riebeckite. The crocido- 

 lite embeds, more or less completely, the quartz and rock fragments. 



Many of the quartz crystals, particularly the larger ones, were at- 

 tached to the walls and included the microcline and aegirite crystals of 

 the pocket lining. Others, and possibly the greater number, were 

 wholly enclosed in, and enclose, the crocidolite, or were attached to the 

 fragments. In fact, the crocidolite is literally crowded with quartz 

 crystals, most of them quite small. Much of the quartz has been 

 strongly attacked by solvent action, the crystals being deeply etched, 

 pitted, and in some instances a good part of a crystal has been dissolved 

 away. Some of the »|uartz is coated with the same black or brownish 

 material noted on the aegirite crystals of the pocket lining. The 

 minerals of the fragments show abundant evidence of solvent action 

 and a later second growth. The riebeckite crystals in particular are 

 often deei)ly honeycombed and in the cavities thus formed are later 

 crystallizations of hair-like riebeckite, ilmenite, quartz, and tluorite. 

 Some of the broken surfaces of the fragments have received a later 

 growth of quartz parallel to the original quartz crystals of the fragment. 

 The hair-like riebeckite, often suspending minute, pierced (juartz crys- 

 tals, frequently form beautiful clusters on the free surfaces of the frag- 

 ments or in small cavities. Crystals of parisite are implanted in the 

 same way on the fragments. Embedded in the crocidolite are casts 

 of original fluorite octahedra sometimes partially filled with a mass of 

 riebeckite fibers and crocidolite originally contained in the tluorite. 

 The casts are generally discolored or partially filled by brown wax-like 

 material. The large riebeckite crystals of the coarse granite or peg- 

 matite bordering the upper portion of the central pocket also show 

 strong corosion. Here the usual lining of microcline and aegirite ap- 

 pears to have been either very thin, or more probably was broken off, 

 since many fragments of coarser pegmatite with aegirite and microcline 

 cr}'stal8 attached to one side are found among the fragments in the 

 pocket. 



