The gradual decline in the production of copper from the mines of Cornwall and the consequent diminution of their number renders any discovery of a rare copper mineral an object of interest to all mineralogists.

Owing to the exhaustion of all the upper deposits, those products of decomposition—the beautiful arseniates and phosphates, &c. which adorn the cases of our national collection and those of private collections—are getting more and more scarce, and perhaps in the near future, so far as Cornwall is concerned, we shall have to rely for illustrations entirely on its past productions.