J^uttaWs Geological and Mineralogical Remarks. 243 



iron, but always accompanied by hornblende rock. One 

 of the most profitable beds of iron ore was discovered on 

 the very spot where the furnace stands ; this highly mag- 

 netic oxyd so much esteemed, is very intimately blended 

 with'plumbago, so as at first glance to resemble the sidero- 

 graphite of Doctor Torrey. In the latter, however, the 

 iron is perfectly metallic ; in this a protoxyd. 



Among the more curious accompaniments of this metal- 

 iferous formation is the brownish yellow garnet, analyzed 

 by Vanquelin, who found it entirely soluble in muriatic 

 acid, which not only takes up the silex contained, but also 

 the manganese, in consequence of its existing in the mine- 

 ral at the minimum, of oxydation. The same substance 

 has now also recently been analyzed by Mr. Seybert. It 

 here forms a bed or vein six or more feet wide, and when 

 occasionally in contact with the carbonate of lime exhibits 

 imperfect dodecahedrons of a lustre and colour almost 

 similar to idocrase. 



Contiguous to the great bed of Franklinite, at Franklin^ 

 is interposed, as it were, in the crystalline carbonate of 

 lime, which prevails to the east, a ledge of imperfect seini- 

 tic granite,* scarcely presenting any thing more than gray 

 crystalline rocks of a binary combination of quartz and 

 felspar. In these rocks occur beautiful opaque blackish- 

 brown masses of garnet, of a high resinous lustre, and 

 crystallized on the surface ; it agrees in every respect, but 

 the unimportant one of direct colour, with the melanite of 

 Frascati, near Vesuvius ; it is accompanied by a lamina- 

 ted epidote almost similar in appearance with the loboite, 

 or idocrase magnesifere of Berzelius. 



Near the same locality there is a vein or two contiguous 

 to the junction of the sienitic granite and carbonate of 

 lime, consisting almost exclusively of a nearly white and 

 compact massive, or minutely lamaller augite, in some 

 parts intimately blended with specks of violet, granular 

 felspar, resembling petrosilex ; also sphene, brown garnet, 

 dark green granular augite, like the coccolite of Lake 

 Champlain ; something of nearly the same colour, and in- 

 fusible, which we suppose may prove the Gahnite, occa- 



*. According to Dr. Maculloch's sagacious defiDition in his geology of 

 Glen Tilt, being here or there, a mere modification of granite, and totally 

 unconnected with the genuine sienite allied to greenstone. 



