180 DESCRIPTIONS OF MINERALS. 



soda bead in the outer flame is colored green by the manga- 

 nese. 



Diff. Resembles magnetic iron, but the exterior color is a 

 more decided black. The streak is reddish brown, and the 

 blowpipe reactions are distinctive. 



Obs. This is an abundant ore at Sterling and Hamburg, 

 in New Jersey, near the Franklin Furnace ; at the former 

 place the crystals are sometimes four inches in diameter ; 

 also amorphous at Altenberg, near Aix-la-Chapelle. 



Chromite. — Chromic Iron. 



Isometric. In octahedral crystals, without distinct cleav- 

 age. Usually massive, and breaking with a rough unpolished 

 surface. 



Color iron-black and brownish black ; streak dark brown. 

 Lustre submetallic ; often faint. H. =5*5. G.=4 , 3-4 , 6. 

 In small fragments attractable by the magnet. 



Composition. General formula RR 4 , as for magnetite ; 

 but part of the iron is replaced by chromium. Analysis 

 gives Iron protoxide 32, chromium sesquioxide 68 = 100 ; 

 aluminum and magnesium also are commonly present in 

 variable amounts, replacing the other constituents. B.B. 

 infusible alone ; with borax a beautiful green bead. 



This ore usually possesses a less metallic lustre than the 

 other black iron ores. 



Obs. Occurs usually in serpentine rocks, in imbedded 

 masses or veins. Some of the foreign localities are the 

 Gulsen Mountains in Styria ; the Shetland Islands ; the de- 

 partment of Var in France ; Silesia, Bohemia, etc. 



In the United States it is abundant : in Maryland in the 

 Bare Hills, near Baltimore, and also in Montgomery County, 

 at Cooptown, in Harford County ; and in the north part of 

 Cecil County ; occurs also in Townsend and Westfield, Ver- 

 mont, and at Chester and Blandford, Mass. It is also found 

 in Pennsylvania, at "Wood's Mine, near Texas, Lancaster 

 County, in West Branford, Chester County ; at Bolton and 

 Ham, Canada East ; in California near New Idria ; also in 

 Sonoma County ; Tuolumne County, near Crimea House, 

 and elsewhere ; at Seattle in Wyoming. 



The compounds of chromium, which are extensively used 

 as pigments, are obtained chiefly from this ore. Meteorites 

 have afforded a chromium-sulphide, named Daubreelite. 



