326 



DESCRIPTIVE MINERALOGY. 



and granular varieties of garnet, tabular spar, green coccolite, and occasionally with crystal- 

 lized hornblende. This locality was first described by Mr. A. E. Jessup.* 



The composition of this colophonite, according to Mr. H. Seybert, is as follows : t 



Silica, 38 . 00 



Lime, 29.00 



Protoxide of iron, 25. 20 



Alumina, 6. 00 



Water, 0.33 



A similar locality exists in the town of Lewis, about ten miles .south of the village of Keese- 

 ville. The specimens can scarcely be distinguished from those obtained from Willsborough. 

 It is, like that just described, an immense deposit of colophonite in large grains, associated 

 with, and apparently passing into, massive garnet of various colours. It is also associated 

 with tabular spar, which, as well as the garnet, is very abundant. 



Several varieties of garnet are found in great abundance at the celebrated Rogers' rock. 

 These, liowever, constantly pass into each other by almost imperceptible shades, and some- 

 times several of them are found in a mass of one or two feet in diameter. In some parts of 

 the deposit, the garnet is in the form of red grains and irregular masses, associated with white 

 feldspar ; in others, the grains are small, loosely aggregated, have a high lustre, and a red- 

 dish yellow colour. This, together with similar grains of a beautiful red colour, belongs to 

 the colophonite variety. Huge masses of a yellowish and reddish yellow colour, and which 

 cleave into plates, are also abundant ; and in the fissures in this variety, interesting crystal- 

 line forms are often found. These crystals have a peculiarly resinous lustre, and a paler 

 colour than is usual. The forms observed arc the primary (Fig. 270) ; the primary with the 

 edges replaced by tangent planes (Fig. 271) ; also the forms represented by Fig. 272, and by 

 Fig. 274, in which six of the faces of the dodecahedron are so much extended as to give the 

 crystal the appearance of a six-sided prism with three terminal planes ; Fig. 275, in which 

 two of the sides are so much enlarged as to present the form of a flattened table ; and also 

 Figs. 276 and 277. 



Fig. 274. 



Fig. 2T5. 



Fj;- 27G. 



Fig. 277. 



* Journal of the AcadcTny of Natural Sciences of Philadelphia. II. 185. 



■f American Journal of Science. V. 118. 



