246 PROCEEDINGS OF THE ACADEMY OF 



Most parts of the rock are devoid of mica, but in some posi- 

 tions an abundance of large crystals of muscovite are mingled 

 with the other constituents. The muscovite, of a smoky color, 

 often contains compressed crystals of tourmaline, mostly olive- 

 green and translucent, simple or compound, and more or less ra- 

 diant. 



Apparently occupying recesses in the common rock, there occur 

 minerals of a difi'erent character. Masses of pink lepidolite, 

 associated with laminar albite, smoky quartz, cleavable masses of 

 ambh'gonite, cookeite, and variouslj^ colored tourmalines; silvery 

 white mica containing apple-green, friable tourmalines; and usu- 

 ally oi^aque greenish or nearly white beryls. 



Contiguous with these curious associations of minerals, pockets 

 are met with filled with decomposed albite, crystals of smoky 

 quartz, detached botryoidal masses of cookeite and tourmalines. 

 The finest specimens of the latter are raked together with the 

 other loose contents from the pockets. They are also found im- 

 bedded in some of the more solid associated rocks, the lepidolite, 

 the cookeite, and the smoky quartz. 



The tourmalines are remarkable, being usually partly colored of 

 various shades of green passing into red, and partially opaque to 

 transparent. Small cr3'stals from half an inch to an inch and a 

 half in length, and from half a line to the fourth of an inch in 

 thickness, occur abundantly imbedded in the cookeite. In spongy 

 masses of the latter, they appear closel}^ invested with thick 

 sheaths of the same substance. These smaller tourmalines are 

 visually bright grass-green, and transparent, but others are nearly 

 colorless, and green or pink at one end. Frequently they are 

 fissured, partially decomposed, and sometimes the decomposition 

 extends along the axis, so as to render the crj^stals tubular. 



The tourmalines of the pink lepidolite usually occur in compa- 

 ratively large crj^stals, firmly imbedded or even incorporated with 

 the lepidolite and albite. These are opaque and brittle, and rarely 

 obtained except in fractured specimens imbedded in the inclosing 

 mineral. They are dark indigo-blue, constituting the variety in- 

 dicolite, but oftener are dark olive-green with a rose-pink exterior, 

 which at times appears gradually to pass into the condition of the 

 surrounding lepidolite. 



The largest and finest tourmalines, obtained from the loose 

 material of the pockets previously mentioned, almost invariably 

 occur in a fractured condition. Two pockets exposed in our pre- 

 sence, communicated with fissures of the surrounding rock, and 

 the contents, as raked forth, were observed to be quite moist. 

 During the winter their contents are probably frozen, and the 

 freezing of water in fine fissures of the tourmalines probably ac- 

 counts for their being usuall3' found in a fractured state. 



The tourmalines of the cavities occur from those of a small size 

 up to such as measure three or four inches or more in length, and 

 from half an inch to an inch and a half in diameter, doubl)^ termi- 



[January 16, 



