the Alps and Apennines in Liguria. 405 
pale colour, and exhibits as its principal constituents abundant large 
and medium-sized elements of quartz, plagioclase, considerably or 
wholly kaolinized, with some orthoclase and subordinate black biotite 
and muscovite. Ina small isolated mass in the north near Pian di 
Burré, about 500 metres altitude, it is more fine-grained and in part 
microgranitic. The granitic rocks, both in their fresh, unaltered, 
and in their far more often altered and friable condition, are well 
exposed along the Savona and Turin railway in the Upper Letimbro 
Valley, in the ravines of the tributary torrents Canova and Porcheria, 
and in Monte Porcheria in the western part of the area. In the 
eastern part interesting outcrops occur on the eastern flank of Monte 
Negino, in the Piantavigna and Montegrosso ravines, and notably in 
the Sansobbia Valley near Ellera, in Monte Ciri, between the Sansobbia 
and Rubiasco Valleys, and in the latter valley between Piazza and 
Vetriera along the road from Albissola to Stella. , 
The gneiss when unaltered is rich in dark brown or black 
biotite with muscovite, and exhibits large orthoclase and plagioclase 
elements together with granular quartz. It differs from the Permo- 
Carboniferous gneiss chiefly in that the latter is more fine-grained, 
with more muscovite, and paler in colour; but the differentiation is 
often very difficult.1 Interesting outcrops of gneiss with associated 
minute gneiss and mica-schist are those along the coast between 
Albissola and Savona, where the gneiss is perhaps more unaltered 
than in other parts of the area; along the Savona and Altare road, 
in the Lavanestra Valley, where gneisses, amphibolites, and granite 
alternate; also on the road from Celle to Ferrari and Sanda, on the 
eastern margin of the area, where the gneiss is in contact with calc- 
-schist and pietre verdi, and in the south-west in the Quazzola Valley 
and on Monte Ciuto. 
The amphibolites are largely derived from pyroxenic rocks with 
uralitized augite and saussuritized felspar, so much so that often 
hardly, if any, trace is left of the original constituents. They «re 
closely associated with the gneissic rocks, and differ from the pietre 
verdi of the cale-schist horizon on the northern and eastern border as 
much as the corresponding rocks of the Piémontese Alps. Of the two 
bands which cross the gneissic masses from south-west to north-east 
the larger one may be traced from the Quazzola Valley to a point 
where it traverses the road between Monte Ciuto and Cadibona, and 
then the Savona and Altare road near Monte Moro in the Lavanestra 
Valley; thence, on the eastern side of the Santuario island to Bric 
dell’ Amore, Monte Cucco, and the Albissola and Ellera road in the 
Sansobbia Valley. The lesser, more southern band, in contact with 
the granitic mass of the Madonna del Monte, crosses the road from the 
latter point to Cadibona south of Monte Ciuto. Some of the best 
exposures of the principal band occur on the ridge from Savona north 
to Crocetta, and towards Monte Negino, where the amphibolic banks, 
notably in Monte Pasasco and north of Monte Cucco, reach a thickness 
of over 400 metres. 
1 The Permo-Carboniferous gneiss is largely developed in the Quiliano and 
Roviasea Valleys, in the Bormida Valley west of Altare, and further north-west 
down to Ferrania di Mare in the same valley; also along the Lavanestra Valley 
in the Savona and Santuario island. 
