Dr. Du Riche Preller—Ophiolithie Rocks, E. Liguria. 493 
or eastern of which includes Mte. Porcile (1,249 m.), Zenone 
(1,072 m.), Alpe (1,096 m.), and Pu (1,007 m.), while the middle one 
comprises Mte. Bianco (876 m.), Rocca Grande (968 m.), Mte. 
Treggin (876 m.), and Mte. Loreto (360 m.), and the western 
descends to 400 and 300 m. altitude. 
The ophiolithic rocks are infolded in the usual Kocene sedimentary 
strata, notably fine-grained, bluish-white, nodulous, and banded 
limestone, and argillaceous schists, frequently tilted almost vertically. 
Serpentines predominate more especially in the eastern, diabase and 
euphodite in the western and central part; their proportion may be 
roughly estimated as being 2/5, 2/5, and 1/5 respectively. The 
northern margin of the group is, between the ophiolithic rocks on one 
side and the calcareous rocks on the other, fringed by bands of 
claret-coloured diaspri up to one kilometre in width, which crop out 
on some of the highest points of the middle and eastern ridges such 
as Mte. Bianco, Rocca Grande, Mte. Treggin, Porcile, and Alpe. 
The principal roads leading from the coast up into the hills are those 
from Sestri to Casarza and Castiglione (271 m.) along the Petronia 
Valley in the southern, and from Lavagna along the Graveglia Valley 
to Nascio (390 m.) in the northern part of the area, as also the roads 
up the Gromolo Valley to the Libiola mine (380 m.), and from Casarza 
to Bargone in the centre of the area. The first of these more 
especially crosses in succession the serpentine, diabase, and euphodite 
masses in a natural section west to east of about 4 kilometres, along 
the Petronia Valley between Casarza and Castiglione. This section 
is very similar to a larger, parallel one across the widest and central 
part of the group from the Gromolo Valley to Rocca dell’ Aquila, 
‘ Rocea Grande, and Monte Zenone, cutting the three anticlinal folds 
and the synclines between them. ‘These sections and another 
interesting one along the Libiola road, showing nodulous diabase, 
and euphodite veins in serpentine, are represented in Figs. 2, 3, and 
- 4.1 Throughout these sections the euphoditic masses more than the 
other rocks are greatly altered, and often decomposed; the contact 
with serpentine is always distinct, while euphodite and diabase 
constantly merge into each other. 
The euphoditic and diabasic masses throughout the area contain 
considerable nodules of copper pyrites which are worked in a number 
of mines, some of whose approach-tunnels afford interesting exposures. 
One of these is notably the Libiola mine above the hamlet of that 
name and in the Gromola Valley on the western margin of the area 
at about 350 metres altitude, in a diabasic island of a serpentine mass. 
The green and reddish diabase here is not only compact but forms 
laccolitic aggregations in which nodules of pyrite are embedded and 
separated from the encasing rock by thin strips of white resinite. 
In another mine on the left of the Gromolo torrent nodulous euphodite 
appears encased in serpentine, which is completely altered to steatite. 
- Manganese is found only in the diaspri bands, while serpentine 
throughout is devoid of metalliferous deposits, as previously stated, 
though they often appear in close proximity to it. 
1 These sections are deduced from LL. Mazzuoli’s in ‘‘ Formazioni ofiolitiche 
della Riviera di Levante, Liguria’’: Boll. R. Com. geol., 1892, p. 2 et seq. 
