468 T, L. WATSON WEATHERING OF ALLANITE 



erals, the rarer ones include tourmaline, garnet, magnetite, columbite, 

 beryl, gahnite, and allanite. Eobinson^^ reported the occurrence of al- 

 lanite in considerable abundance, and in the form of brownish crystals 

 partially decomposed, resembling rusty nails driven into the granite. 

 Analyses of the allanite^* from this locality are given in the table on 

 page 474. 



Massachusetts. — In Massachusetts allanite occurs fairly well distributed 

 as a constituent of certain igneous rocks, especially granite, and of some 

 pegmatites. One of the most interesting occurrences of the mineral is 

 at the asbestos mine at Pelham, where, according to Professor Emerson,^^ 

 it is a constituent of the macroscopic "reaction rim" between the dike of 

 black olivine-enstatite rock and the inclosing gneiss. Here it occurs 

 abundantly in granular anorthite in crystals up to 2 inches long and 

 one-half inch across. Professor Emerson has also recorded allanite from 

 a number of localities in Hampshire and Franklin counties. It is a con- 

 stituent of the Hatfield tonalite and of the Pelham gneiss, but the finest 

 crystals are found at Gilbertville in coarse granite. At Buckland, south 

 of the Harris soapstone quarry, allanite occurs superficially altered to a 

 red substance. This is probably the alteration product of allanite due to 

 weathering discussed for other localities in this paper. 



Dale^^ reports allanite as an original accessory mineral in the granites 

 of Quincy, Milford, Eockfort, and Becket, that of the Milford granite 

 being rimmed in several instances with epidote. An interesting asso- 

 ciation is that of allanite with magnetite, ilmenite, epidote, zircon, 

 fluorite, quartz, etcetera, in the segerite and riebeckite pegmatite masses 

 of the Quincy granite, the rare forms of amphibole and pyroxene being 

 of unusual size.^^ 



The occurrence of allanite in the granite of Essex County has been 

 noted by Balch,^^ Iddings and Cross,^^ Sears,^^ and Washington,^^ and an 

 analysis of the mineral from Swampscott^^ is given in column lY of table 



13 F. C. Robinson : Am. Jour. Sci., vol. 27, 1884, p. 412. 

 " F. C. Robinson : Am. Jour. Sci., vol. 27, 1884, p. 412. 

 F. W. Clarke : Am. Jour. Sci., vol. 28, 1884, p. 20. 



15 B. K. Emerso^i: Bull. 126, U. S. Geol. Survey, 1895, pp. 14-3 5; Bull. Geol. Soc. Am., 

 vol. 6, 1895, p. 474 ; Mono, xxix, U. S. Geol. Survey, 1898, p. 754. 



16 T. N. Dale: Bull. 354, U. S. Geol. Survey, 1908. 

 " T. N. Dale : Ibid., 1908, p. 50. 



C. H. Warren and C. Palache : Proc. Amer. Arts and Sci., 1911, pp. 125-168. 

 18 D. M. Balch : Am. Jour. Sci., vol. 23, 1862, p. 348. 

 10 J. P. Iddings and W. Cross: Am. Jour. Sci,, vol. 30, 1885, pp. 108-111, 



20 J. H. Sears : Bull. Essex Inst., vol. 26, 1894, p. 189. 



21 H. S. Washington : .Tour. Geology, vol. 6, 1898, pp. 787-808 ; see especially pp. 792- 

 793. 



22 D. M. Balcb : Loc. cit, p. 348. 



