oj Copper and of Iron. 5 



U-hen a piece is frefli broken, is a deep yellow ; and this 

 yellow colour is more deep in proportion as the quantity of 

 copper is more abundant. In its richeft ftate, it affumes a 

 more or lefs greenifli tint. The furface of a frefli frafture is 

 very brilliant, and appears rather uneven, as if compofed of 

 fmall laminse crofling one another in an irregular manner. 

 When it betiins to decompofe, its furface is covered with the 

 moll beautiful colours ; among which the mod: predominant 

 arc, violet, blue, and green: this has caufed it to be com- 

 pared to a pigeon's breaft. -When thefe colours are- very 

 deep, and occupy the whole furface of a piece, we commonly 

 perceive, here and there, fome little points in the ftate of red 

 oxide of iron; and others of a green golour, in the ftate of 

 green carbonate of copper. 



This kind of copper ore is fometimes of a deep yellow 

 colour, which inclines the more to green, as it is deftitute of 

 brilliancy, [t is very compaft, and, when broken, the frac- 

 ture appears fmoolh, fometimes a little conchoidal; its fur-' 

 face, however, has a very- fine grain, which, when viewed 

 with a powerful lens, refembles the aggregation of a very 

 clofe compa6l mafs of the fineft fand. Its mod ufual texture 

 is that of thin layers or plates, lying one upon another, and 

 being very clofoly united, fo as to be fcarcely perceptible to 

 the naked eve ; but they are very readily diftinguifhed with. 

 the lens. Thefe layers, however, do not adhere very ftrongly, 

 as they may always be feparated by the ftroke of a hammer. 



This ore frequently aflumes a mamillated form j the ma- 

 milUe being of different dimenftons, from the fize of a man's 

 head, and even larger, to that of a fmall pea. In the latter 

 cafe, the rnamillae are very often united, as in that kind of 

 iron ore which is called clufter, botryoid, or kidney hematites. 

 Sometimes "the furface of the rnamillae is covered with fmall 

 points ; but more frequently it is fmooth, fo as very much to 

 relemble a piece of poliflied metal ; and, as the furface of the 

 rnamillae inclines rather to a brown colour, they have the 

 appearance of antique bronze. The green oxide of copper, 

 which fometimes. is obferved on it, completes the illufion, by 

 afluming the afpcA of that fine patina which often coverg 

 pieces of antique bronze. 



This ore is likewife found in the form of fmall cylinders, 

 often placed one againft the other, and fometimes ramified, 

 in the fame way as is obferved in fome kinds of hematites. 

 When the broken furface of it is expofcd for fome time to 

 the air, it aflumes the colour of tarnidied gold. It acquires 

 alfo, by the decompofuion of its furface, the fame violet, 

 A 3 blue. 



