312 Dr. Dw Riche Preller—Crystalline Rocks, N. Prémont. 
peak, where the pietre verdi rocks contain fine specimens of gastaldite 
(blue glaucophane) and garnet crystals. The Permo-Carboniferous 
diorite and gneissiform schist zone of the Savaranche and Cogne 
Valleys is obviously connected with the similar diorite of Locana in 
the Orco Valley and of the Ivrea and Val Sesia belt to be dealt with 
later. 
2. Monte Emilius (Fig. 1).—A striking contrast to the normal 
sequence of the crystalline sedimentary and pietre rocks of the 
Grivola group is presented by Monte Emilius (3,559 m.) and the 
neighbouring Becca di Nona (3,182 m.), which lie about 12 kilometres 
south-east ot Grivola, and are separated from the latter by the Cogne 
Valley. Both mountains, with their extremely rugged and craggy 
flanks, rise straight from the Dora Baltea Valley between Aosta 
(580 m.) and St. Marcel to a height of 3,000 and 2,600 metres 
respectively in a horizontal distance of barely six kilometres. The 
upper parts and summits of both are composed of minute gneiss and 
eclogitic, garnetiferous mica-schist, while the lower flanks facing the 
Aosta Valley consist of huge masses of coarse-grained, gneissiform 
euphodite more or less parallel to the overlying gneiss and mica- 
schist. On the Monte Emilius flank the encircling cale-schist 
formation is not in direct evidence, but on Becca di Nona it crops 
out above Charvenod close to Aosta and again higher up at the 
Sismonda signal (2,347 m.), where it rests on minute gneiss. In 
both places the cale-schist dips at a steep angle in opposite directions, 
while the gneiss and mica-schist of the upper flanks and summits of 
both mountains are greatly contorted; near St. Marcel, at the lower 
end of the valley of that name, they descend to the 700 metres 
contour and then apparently dip below the calc-schist. 
The phenomenon of reversed sequence in the Monte Emilius group 
is the result of an inverted fold in connexion with the great fracture 
fault which runs along the Aosta Valley to Chatillon and St. Vincent. 
From here, instead of following the sharp southward bend of the 
Dora Baltea towards Ivrea, it extends east across the Brusson Valley 
to Arcezas, where the calc-schist mass at the base of a great gneiss 
bank affords striking proof of a similar dislocation near the Conte . 
with the mica-schist formation of the Ivrea belt. 
8. Monte Rafré (Fig. 1).—About 12 kilometres east of Monte 
Emilius, in the calc-schist and pietre verdi area of the Clavalité and 
Champorcher Valleys previously mentioned, occurs the remarkable 
sequence of the Monte Rafré (3,146 m.) and Monte Glacier (3,186 m.) 
group which forms the divide between those two valleys. In this 
case, a mass of brecciated prasinitic gneiss which crops out on the 
crest of the divide, overlies a mass of euphodite metamorphosed to 
prasinites, in apEanenuy reversed sequence. In reality the prasinites, 
as Stella has shown,! are an isolated lenticular wedge intercalated in 
the brecciated gneiss which lies in the calc-schist formation. ‘The 
latter, with pietre verdi, extends from the Champorcher Valley to 
1 A. Stella, ‘‘Gneiss Monte Emilius e M. Rafré’’: Boll. Soc. geol. ital., 
1906, p. xlvi. E. Mattirolo, ‘‘ Rilevamento Val Champorcher, Alpi Graje’’: 
Boll. R. Com. geol., 1899, p. 3 et seq. 
