466 MINERALS IN THE [December, 



borax it forms a yellowish brown glass. It is frequently 

 attached to organic remains. The massive or earthy va- 

 riety, is said to occur in pieces of thirty pounds weight at 

 AUentown, N. J. When first exposed to the atmosphere, 

 it presents a white appearance, but soon changes to a fine 

 sky blue. It is affected by the blowpipe as the crystal- 

 lized. Professor Cooper has lately proved this to be a 

 hydrat, and not a phosphat of iron. Its solutions in nitric 

 acid, do not precipitate the solutions of lead. 



Arsenical Iron. Arsenical Pyrites. W. Marcasite, K,^ 

 Fer arsefiicaL H. 



A piece of this mineral of nearly two pounds weight, 

 was given me by a person on Perkiomen, who informed 

 me it was found in the neighbourhood. Colour, yellowish 

 white, fracture uneven. When subjected to the blowpipe, 

 the arsenic was volatilized in a white vapour, giving out 

 a strong alliaceous odour. 



Chromate of Iron, Fer chromatL H. 



This combination of chromic acid with iron, is found 

 in the talc rocks of Chestnuthill, where it is generally 

 accompanied with small fibres of asbestus. Colour, rather 

 darker than steel gray. Some of the more impure vari- 

 eties give a singular appearance to the rocks there. They 

 present dark spots from one quarter to three or four inches, 

 disseminated throughout. It is also found in a verj^ pure 

 state in steatite rock, on Lewis's farm, near the West- 

 chester road, about ten miles from the city, and near the 

 Lancaster turnpike, about the same distance. From the 

 two last localites it is used in the arts here. \ 



