436 A. S. Fakle — Allanite Crystals from JVeiv Jersey. 



Art. LIII. — On Allanite Crystals from Franklin Furnace, 

 N. J. ;* by A. S. Eakle. 



Allanite, as a rock constituent, has been shown to be very- 

 widespread in its occurrence and the crystal] ographic proper- 

 ties of the mineral from many localities, have been determined. 

 The present article is the result of an examination of a large 

 number of crystals coming from the Trotter Mine, Franklin 

 Furnace, JN. J. 



The presence of allanite at Franklin Furnace was first re- 

 ported in 1850, by C. T. Jackson, f who published a short 

 description of its occurrence and an analysis. His crystals 

 came from a different locality, being in the feldspar of the 

 old magnetite mines, while those described here occur with 

 the zinc ores, in a great granite dyke4 



The crystals are coal-black in color, Very brittle, and occur 

 in the common, flat, tubular forms, elongated parallel to the 

 ortho-axis. The faces of the crystals are, in general, dull, and 

 when magnified appear to be much pitted, so that reflections 

 with the Fuess goniometer are poor. Imperfect cleavage 

 occurs parallel to the basal- and ortho-pinacoid faces and more 

 perfect in the direction of the prism face, but varying about 

 6° 30' from parallelism. An average of several readings gives 

 an angle of 4-7° 56' between this cleavage face and the ortho- 

 pinacoid. 



Fourteen forms, in all, occur on the crystals, none of them, 

 however, being new. The forms are the following : 



a = coP^5(ioo) n— P (111) 



C = OP (001) 0= Poo (Oil) 



d = — P (111) r— Poo (101) 



e = — P^d (101) u — ooP2_ (210) 



i — £Pot ( l02) w = -2P2 (211) 



I — 2~Po5 (201) S = ^Po5 (103) 



m= ooP (110) x = — ^P^(102) 



The forms x, i and o are less common, and w and s are rare. 

 The remaining faces are quite common to the species, not alone 

 in this locality, but in general. On the " bucklandite " (allanite) 

 of the Laacher See,§ and later on the allanite from Vesuvius,! 

 Dr. G. vom Rath has described a large series of forms, most 



* Published in the Trans. N. T. Acad. ScL, Nov. 27. 1893. 



f Allanite from Franklin Furnace, X. J . C. T. Jackson. Proc. A. A. A. S., 

 1850, p. 323. 



X Kemp, J. F., Trans. N. Y. Acad. ScL, Oct. 30, 1893. 



§ G. vom Rath, Ueber die Krystallform des Bucklandits vom Laacher See, 

 Pogg. Ann. Phys. und Ch.. vol. cxiii, p. 281. 



I Or. vom. Rath, ibid., vol. cxxxviii, p. 492. 



