298 GEOLOGY AND MINERALOGY. 
London.* Although so different in geological age, the district described by Mr. 
Jervis appears to have many characters of a more or less general resemblance to 
those of our Eastern Townships. After describing the products, é&c., of four dis- 
tinct eruptions of Serpentine, Mr. Jervis proceeds as follows :— 
“The topographical appearance of the serpentine-eruptions is very character- 
istic ; there is an entire absence of those undulating chains or eminences, melting 
insensibly into one another, which enable us to ¢lassify hills into groups. These 
rocks form dykes, but more generally constitute whole hills of conical form, 
rising abruptly to a considerable height, and terminating in rugged, sharp summits. 
The older rocks have been much upturned and elevated, and are thrown off in 
every direction,—the serpentine, forming the nucleus of the mountains so abundant 
along the west coast of Tuscany, Modena, and Piedmont, generally reaching the 
surface somewhere near the centre, and forming (if I may be permitted the ex- 
pression) a “ periclinal” axis. 
The older rocks, nearer the focus of action, are the most disturbed. No feature 
regarding this serpentine is more important than that of its being almost 
invariably accompanied by rich ores of copper at its junction with the metamor- 
phosed schists or gabbro rosso. These two rocks, similar in name, are entirely 
distinct in most other respects : one is an aqueous, the other an igneous rock. 
Many minerals are peculiar to the junction of the gabbro rosso and the Miocene 
serpentine ; they are chiefly zeolites. The commonest is eapprcianite, a white 
crystalline mineral, tinged with pink, in structure resembling analcime. These 
zeolites all contain magnesia. They are,— 
Magnesia Magnesia 
: per cent. : per cent. 
Savite, containing ........ 13°50 Portibel oc. oe oe we elec aimne 4°87 
Schneiderite ..... Siete siete 11°03 Sloanite 2241s .<‘ee jae. cies se 
icranalcimenseceseccees  LOW25 Humbolutite) 2.\5<cicjs1e = eietse cen 
Picrothomsonite.........-- 6°27 Caporcianite......sesese-- LSE 
Miemite (dolomite) contains 42°5 per cent. of magnesia; “ gabbro,” from La 
Spezia, 244. 
Calcareous spar also occurs in limpid and extremely obtuse rhombohedral 
crystals; it probably owes its origin to the metamorphosis of the limestones. I 
consider all these minerals to have been produced at the period of the intrusion of 
the Miocene serpentine, from whence they doubtless derived their magnesia. Itis 
also interesting to find that large quantities of the limestone in the neighbourhood 
have been altered into dolomites,—the miemite, a delicate greenish rock of the 
same colour as aquamarine, being a double carbonate of lime and magnesia. 
The copper from the serpentine is not associated with galena and blende as © 
with us, but is accompanied by many asbestiform minerals. 
The action of the serpentines on the limestones which they have traversed is 
very varied. Near Matarana I noticed the action on a mouse-coloured limestone, 
where peroxide of iron had imparted a brick-red tinge to various parts of the 
* On certain Rocks of Miocene Age in Tuscany, including Serpentine, Copper Ores, 
Lignite, and pure Alabaster used in Sculpture. By W. P. Jervis, Esq., F.G.S. Quarterly 
Journal of the Geological Society. (Vol. XVI.) No. 64 
