GEOLOGY AND MINERALOGY. 299 
mass. Within a yard or two of tbe serpentine the rock had been apparently 
broken into fragments, which had been eemented by delicate veins of serpentine 
flowing into and filling up the cracks. This beautiful metamorphic rock, called 
‘“Ofiocalce,” is, in fact, ealeareous serpentine: it forms a rich combination of 
eolours—deep red and dark green, with interlacing veins of pure-white calcareous 
spar. I would offer this explanation: total decomposition of the limestone was 
prevented by the pressure; the carbonic acid was partially expelled ; the heat 
decomposed the carbonate of iron which was present in minute quantities, and 
completely peroxidized its protoxide of iron, which, being no longer isomorphous 
with the pure carbonate of lime, was rejected as the latter crystallized out in 
various parts. If Iam not mistaken, this would prove that the crystallization of 
carbonate of lime in prisms (as arragonite) only takes place within limited degrees 
of temperature, above and below which the crystalline system is the Hexagonal. 
The copper-mire of Monte Catini is found at the junction of the gabbro rosso 
and the Miocene serpentine; the ore is invariably in the latter. It is one of the 
finest to be seen anywhere, and [its working] dates at least from the Florentine 
Republic, Cosmo I. re-opened it in 1562; but it was not regularly worked, and, 
from want of experience, little was done until 1837. The indications appear to 
have been very favourable at the outset; but the successive proprietors failed to 
realize their desires, until the present company sunk to a depth of 400 feet, 
following the indications of ore or “vein” lying E. and W., dipping at an angle 
of 45° S.; they then found an immense mass of copper-ore, from which they 
extracted 330 tons ; about 100 feet lower a second deposit has lately been reached, 
the breadth of which I should estimate at 60 feet. The various ores of copper 
are met with in rounded masses, enveloped in serpentine ; these nodules constitute 
a species of conglomerate,—some of the masses being ore, others boulders of 
serpentine, dispersed through a matrix of steatitic clay. The nodules on being 
broken open are found to contain chaleopyrites, or bornite,* more rarely oxide of 
copper, grey copper, and native copper. In physical appearance the chalcopy- 
rites differs entirely from that obtained from our mines: tkns it is not lamellar or 
erystallized, but hard, compact and massive, and has precisely the same structure 
as bornite, into which it insensibly passes in the same nodules. This pyrites is 
not mixed up with gangue, but perfectly pure, which can be accounted for by the 
expulsion of impurities, favoured, as it must have been, by the nodular condition 
of the masses. The friction has produced a considerable quantity of fragmentary 
pyrites of the size of gravel, which is all washed and employed. I believe I am 
correct in asserting that iron-pyrites is nowhere found with the serpentine, even 
along with the ores of copper. One of the greatest advantages in working these 
mines is the softness of the steatitic rock. Other mines are established at Lib- 
biano, Monte Castelli, &c.: they are newer, and have been hitherto less fortunate. 
Most probably, as Professor Pilla observed, the deposits whence the rich outlying 
indications proceeded will be met with further down. 
Closely associated with the serpentine, chalcedony is found in large quantities 
* Purple Copper Pyrites,=Hrubesciteof Dana, Phillipsite of Betidant and Dufrenoy.— 
E. J. C. 
