TAB. LXXXVIL 



FERRUM arseniatum. 

 Arseniate of Iron. 



Class 3. Metals. Ord. 1 . Homogeneous. 



Gen. 6. Iron. Spec. 8. Arseniate. 



Div. 1. Crystallized. Far. Primitive. 



Spec. Char. Combined with arsenic acid. 

 Syn. Arseniate of Iron. Bournon in Phil. Trans* 

 1801. 



J his was mostly confounded with arseniate of copper 

 until the celebrated Chenevix, by analysis, ascertained it to 

 be an arseniate of iron : see Phil. Trans, for 1801. Count 

 Bournon observes that it crystallizes in cubes rarely a little 

 flattened: I may add rarely lengthened. I, however, have 

 it a little so, perhaps the fourth of its diameter ; and his 

 figure conveys that idea, although I suppose unintention- 

 ally. The sides, he observes, are smooth and brilliant. I 

 am happy to add another character, that they are diagonally 

 striated in alternate order on each face; this is readily seen 

 in most of my specimens*. They are often a little concave 

 in the centre, and rising to the edges in the longitudinal 

 direction of the striae, and also show signs of being formed 

 on cubical nuclei. I have them from a light yellowish 



* See Ferrum sulphureum, tab. 63, in which the striae are parallel to the 

 edges of the cube ; and Count Bournon has discovered a new species of 

 cubic oxide of iron with the striae at right angles, parallel to every edge of 

 the cube : perhaps these striae may become marks of importance 



