66 THE ROMAN COMAGMATIC REGION. 
of both orthoclase and labradorite with some olivine, from the name of the dis- 
trict. The type adjective is based on the locality, Fontana di Fiescoli, whence the 
original type specimen of ciminite came. 
In the prevailing classifications these rocks have been given a wide diversity 
of names, almost every geologist who has studied the district having chosen a dif- 
ferent one. Thus vom Rath calls them trachytes, Deecke augite-andesites, in both 
cases accompanied by remarks on their anomalous mineralogical and chemical char- 
acters; Bucca speaks of them as trachytes, Mercalli first called them oli vine-trachytes 
and later olivine-andesites, while the name selected by Sabatini is "labradorite," 
used with the French signification. 
In view of this confusion, which amounts to a tacit admission that the type 
belongs neither to the trachytes nor to the andesites, a special name seems advisable, 
and that formerly selected, "ciminite," is appropriate, as the rock is abundant at 
Monte Cimino and was at the time the only one which it seemed to be worth while 
to name. For these reasons Mercalli's recent criticism of the name "ciminite," on 
the ground that the rock does not make up the main part of Monte Cimino, seems 
to be somewhat strained. 
FIESCOLAL CIMINOSE. II. 5. 2. 2. 
Megascopic characters. Medium gray, compact, somewhat porphyritic. Feldspar pheno- 
crysts few, i to 5 mm., tabular or prismatic. Olivine phenocrysts rather abundant, i to 2 mm., 
yellow. Augite phenocrysts rather abundant, i to 2 mm., stout prismatic, black. Ground- 
mass: rather light to rather dark gray, aphanitic. 
Specific gravity 2.70 at 10. 
Microscopic characters. Holocrystalline, rarely percrystalline, mediophyric, dopatic. 
Phenocrysts: about 25 per cent, olivine, augite, orthoclase, labradorite. Groundmass: about 
75 per cent, orthoclase, labradorite, augite, olivine, magnetite, apatite, glass in rare cases. 
Groundmass, texture felted. 
Orthoclase, about Or 4 Abj. Phenocrysts: about 3 per cent, i to 5 mm., subhedral stout 
prismatic or tabular, Carlsbad twinning common, inclusions few. Groundmass: about 40 or 
45 per cent, 0.02 to o.iomm., partly subhedral to anhedral, slender prismatic, arrangement 
diverse, partly anhedral, interstitial cement. 
Labradorite, AbjAnz. Phenocrysts: about 3 per cent, i to 5 mm., subhedral to anhedral, 
stout prismatic, much twinned, often clustered, inclusions few. Groundmass: about 10 per cent, 
0.02 to o.iomm., anhedral, prismatic, arrangement diverse. 
Augite Phenocrysts: about 9 per cent, 0.2 to 2.0 mm., subhedral to anhedral, stout 
prismatic, often fragmentary, colorless or very pale greenish, few inclusions. Groundmass: 
about 15 per cent, o.oi to 0.05 mm., anhedral, slender prismatic, colorless. 
Olivine. Phenocrysts: about 10 per cent, 0.5 to 2.0 mm., subhedral, stout prismatic, 
tabular or equant, often corroded, colorless, commonly with narrow border of yellow iddingsite. 
Magnetite. Groundmass: about 2 per cent, o.oi to 0.02 mm., anhedral, equant. 
Apatite. Groundmass: about i per cent, subhedral, slender prismatic. 
Glass. Usually absent: about 5 per cent, colorless, interstitial between feldspar laths, 
difficult to detect. 
Chemical composition and norm as above. 
Type specimens from Fontana Fiescoli and from La Colonetta, Cimino Volcano, Ciminian 
District. 
