404 



DESCRIPTIVE MINERALOGY. 



ness from 5 . 5 to 6 . 0. Specific gravity from 3 . 82 to 4 . 06. Before the blowpipe on charcoal, 

 it fuses with slight intumescence into a black globule, which is strongly attracted by the mag- 

 net, if not heated to redness ; with borax, it melts into a dark green and almost opaque glass. 

 It forms a jelly with heated muriatic acid. 



Composition. Protoxide of iron 52.54, silica 29.28, lime 13.78, oxide of manganese 

 1.59, alumina 0.61, water 1 .27 («S^rowieyer). 



Geological Situation. The principal locality of this mineral is the island of Elba, where 

 it is found associated with epidote, garnet and iron ore, in limestone. It has also been met 

 with in Norway and Siberia. 



LOCALITIES. 



According to Dr. Emmons, this species occurs in Essex county ;* but I am not acquainted 

 with the precise locality, nor can I give any further account of it. 



Ilvaite or yenite, according to Shepard, has been found at Cumberland, Rhode-Island, in 

 slender crystals in quartz, associated with hornblende and magnetic iron ore. 



SILICATE OF IRON. 



Description. In the slag from the furnace for the cementation of steel, at Ramapo in 

 Rockland county, there are often found cavities lined with short four and six-sided prisms 

 with dihedral summits, as in Fig. 479. They have an iron black colour and metallic lustre, 

 slightly magnetic. Easily fusible by the blowpipe into a bright iron-blue globule, which is 

 attracted by the magnet. 



Fjg. 479. 



Composition. Protoxide of iron 70.00, silica 30.00. It is therefore a silicate of iron: 

 FeO.SiO,. 



This mineral has the same composition as the anhydrous silicate 

 of iron of Thomson, but the latter is said to be infusible by the 

 blowpipe. It is, however, exactly similar to the artificial silicate 

 described by Mitscherlich as formed during the refining process of 

 cast iron, and which has the crystalline form of peridot, Fig. 479, 

 The primary being a right rectangular prism. t T on n 114° 6'; 

 T on A 138° 31'. 



The same product is noticed by Beudant, under the name of 

 peridot with a base of iron.J 



• JVew-Fori Geological Reports. 1839. 



t Brewster's Edinburgh Joumiil of Science. II. 129. — In this paper, Prof. Mitscherlich notices the occurrence of scoriao at 

 Fahlun and Garpenberg in Sweden, and in several of the foundries of Germany, possessing the same form and composed of 

 the same elements as certain minerals found in nature. 



X Traite des Essaui par la Vote Seche. I. 445. 



