1864, Anstep on Copper Mining in Tuscany. 435 
yi f y 
secondary rock, but the actual date of the fissure and its filling up 
must be comparatively modern in both cases. All these Italian mines 
differ in a striking and even startling manner from those of Cornwall 
and other parts of the British Isles. They are quite as different from 
the copper mines of Germany and Scandinavia. They introduce us to 
the phenomenon of a great accumulation of copper ores of the ordinary 
kind (copper pyrites), in veins in comparatively modern volcanic rock, 
these veins having been formed long after the older tertiary rock had 
become deposited and hardened. 'The cretaceous rock, and even the 
older tertiaries had been in some cases elevated before the formation 
of the fissures now filled up with lava, and the lava had cooled and 
solidified and cracked before the copper made its appearance. 
The mine of Monte Catini (della cava) is worked in a very peculiar 
vein of soft magnesian rock (approaching serpentine in its nature, but 
much softer), occupying a dyke or fissure in the gabbro, which is 
apparently itself an eruptive rock originally forced through, over, and 
amongst the upper cretaceous limestone of Tuscany, here called albe- 
rese.* The alberese is a compact pale blue, or greyish blue limestone, 
hard and penetrated with numerous strings of calc spar. It occupies 
the hills and neighbouring high ground, but is generally covered with 
a soft marly rock, often containing gypsum, and sometimes rock salt. 
The latter mineral is abundant, and is worked in the Saline in the 
valley of the Cécina adjacent. 
The alberese is a cretaceous limestone, and the overlying soft marl 
are tert'ary. It appears to me that there has been an eruption of 
igneous rock through fissures in the alberese at a time when the tertiary 
deposit was much more extensive than it now is. Thrust up through 
this rock, which is locally squeezed, contorted, and broken, and form- 
ing a dyke in the soft tertiary clays above, the nearest adjacent clays are 
converted into shales, which are hard and compact enough where they 
approach the igneous rock. In certain places the flow of lava has been 
through two nearly adjacent fissures, meeting one another, and leaving 
at and near the place of contact large open spaces. In the course of 
time the softer earth on each side of the vein has been washed away, 
and there is now left on the flank of the mountain little more than the 
hardened and altered rock. This forms the nucleus of gabbro, which 
here consists of irregular rounded lumps of hard, compact rock, resem- 
bling greenstone embedded in a kind of soft porphyritic mass, weather- 
ing rapidly on exposure, and easily removed underground. This 
gabbro looks much like a true serpentine (pale greenish crystals in a 
dark green bed), and is evidently highly magnesian. 
It is in fissures closed towards the surface, and there presenting 
nothing but reddish clays, which, however, are easily distinguished 
from the gabbro, that we find the only indications of the rich lodes, or 
rather pockets, existing below. It is believed that in former times 
* The name alberese is given both to the chalky limestones of the upper part 
of the cretaceous series, and also to the similar rocks of the upper part of the 
eocene tertiaries. It expresses mineral character. At Monte Catini the a/berese 
of the cretaceous period is thrust through the alberese of the tertiary period, and 
they are in contact. 
