136 



Field Columbian Museum — Geology, Vol. III. 



(ilo) 



(2I0) 

 (120) 



(13°) 



(oil) 



(III) 



(113) 

 (114) 



(122) 

 (122) 



BERTRAND1TE 



ALBANY, MAINE 



FIGS. 4-5, PLATE XLVII 



In the summer of 1902, Mr. C. C. Spratt, at that time a resident of 

 North Bridgton, Maine, submitted to one of the authors some hand 

 specimens showing small, colorless crystals, which proved on examina- 

 tion of their blowpipe characters to be bertrandite. Mr. Spratt 

 kindly indicated the locality from which the specimens were obtained 

 and this was later visited by one of the authors. The locality is an 

 area of coarse pegmatite in the northern part of the town of Albany, 

 Maine. The pegmatite exhibits the usual coarse crystals of quartz, 

 feldspar, tourmaline, mica, and beryl and has been worked to some 

 extent to obtain the two latter minerals for economic purposes. The 

 bertrandite was nowhere found to be abundant, but by close searching 

 could occasionally be obtained. It occurs in single or grouped crys- 

 tals implanted upon quartz or lining cavities one or two inches in 

 diameter. In one of these cavities a considerably corroded piece of 

 colorless beryl was found suggesting that the bertrandite may have 

 been derived from alteration of the beryl. The crystals of bertrandite 

 obtained (Mus. No. M 6969) are for the most part colorless to pale 

 white and transparent to translucent. Some are covered with a rusty 

 coating which readily dissolves in hydrochloric acid. The crystals all 

 show a tabular habit produced by extensive development of the basal 

 planes. In habit they thus resemble the crystals of Mt. Pisek and 

 Mt. Antero rather than those described by Penfield * from Stoneham, 

 although the latter locality is near Albany. The largest crystal of 



* Am. Jour. Sci., 1889, 3, 37, p. 214. 



