IRON. 399 



faces of the crystal are somewhat curved as in pearl spar. Before the blowpipe it decrepi- 

 tates, but at length becomes of a darker colour, and is slightly attracted by the magnet. It 

 is soluble with effervescence in dilute muriatic acid. An analysis gave the following results : 



Carbonic acid, , 45.00 



Lime, „..o« 28.00 



Magnesia, 1 3 . 75 



Protoxide of iron, 11. 25 



Moisture and loss, 2. 00 



Except in the absence of a small proportion of manganese, the above composition is quite 

 similar to that of the ankerite by Bcrthier above given.* 



Specimens resembling the above, are also found in the rock accompanying the iron ore at 

 the Parish ore bed in St. Lawrence county. But the carbonate of lime and carbonate of iron 

 are so liable to accidental mixtures, that the minerals having this composition require to be par- 

 ticularly examined. 



In Massachusetts, ankerite is said to have been found in the coal formation at West-Spring- 

 field. 



COPPERAS. 



For Sulfate. Haiiij. — Sulphate of Iron. Clcavdand and Phillips. — Copperas. S/ifjiurd. — Hemiprismatic Vitriol. 

 Jameson. — Hcmiprismatisclies Vitriol-Salz. Muhf. — Mclantcrie. Bcudant. 



Fig. 4(4. Description. Colour various shades of green passing into white, but more 



frequently, owing to exposure, it is externally of a yellow or yellowish brown 

 colour. Streak white. It occurs massive, pulverulent, and in stalactites. By 

 solution it may be obtained in crystals, the primary form of which is an oblique 

 rhombic prism. Fig. 474. M on M' 82'^ 21' ; P on M 99° 23'. Cleavage 

 parallel to P perfect, less so parallel to M. Fracture conehoidal. Lustre 

 vitreous. More or less translucent or transparent. Hardness 2.0. Specific 

 gravity from 1 . 84 to 1 . 97. Before the blowpipe on charcoal, it becomes mag- 

 netic, and colours glass of borax green. Its solution in water becomes black 



on being mixed with the tincture or infusion of galls ; and with chloride of barium, it gives an 



abundant white precipitate. 



Composition. Protoxide of iron 25.70, sulphuric acid 28.90, water 45.40 {Berzelius). 

 The formula of pure copperas is FeO.S03 + 7Aq. 



Geological Situation. It is almost always found associated with iron pj'rites, from the 

 decomposition of which it has its origin. It most frequently accompanies coal. 



After the statement that has been made in regard to the occurrence of this species as the 

 result of the decomposition of iron pyrites, it will not be necessary to refer to particular 



* TraUi- ih's Kssais par la voic sr.chc. I. -19]. 



