140 
THE ROMAN COMAGMATIC REGION. 
CALCULATED. 

MEASURED. 
41 .0 
Units 
2,O^s 
Vol.%. Sp.gr. 
= 44 .9 X 2.5 = 
1 12 . I 
Wt. %. 
^8.6 
Anorthite 
3-6? 
Nephelite 
73 
460 
= 10. i X 2.6 = 
26.3 
9.1 
Augite 
22 .6 ) 
Olivine 
6.8 \ 
L493 
= 32-7 X 3-3 = 
107.9 
37-2 
Melilite 
12 6 
40 ? 
= 8.8 X 2.9 = 
2C C 
8 8 
Magnetite ... 
A. O 
1 60 
= T, ; X s 2 
18 2 
6.7 
Apatite 
I . 2 
IOO.O 
4,57i 
IOO.O 
290.0 
IOO.O 
The correspondence between these is not very close, though they agree in the 
main features. It would seem that overlapping has entered to a considerable 
extent, and possibly that the section examined was not quite as rich in melilite as 
the mass of the rock. On the whole the mode is normative, but the notable amount 
of melilite should be considered, and the rock may therefore be described as a 
normative melilitic grani-albanose. 
Occurrence. This type is rather common in the Latian District, not only at 
the well-known locality of Capo di Bove, but at Tusculum, near Grotta Ferrata, 
and elsewhere. Rocks which may be considered to be of the same type are also 
found at Poggio Selva and as blocks in tuff at Madonna d'Oro, both near Monte- 
fiascone in the Vulsinian District, and at the fountain west of Trevignano in the 
Sabatinian. 
Name. The type name is derived from the type locality of Capo di Bove, 
between Rome and the Alban Hills. 
In the prevailing systems this type has been uniformly included among the 
leucitites, of which it is always cited as the most prominent example. In view of 
the very considerable amount of melilite, and the interest due this mineral on account 
of its rarity, it might be well to revive Cordier's* old name "cecilite," derived from 
the tomb of Cecilia Metella above the quarry of Capo di Bove, for the melilite- 
bearing leucitites. Such a distinction would be advisable, since the great majority 
of the leucitites are free from melilite, as we have seen. The term "cecilal" can not 
well be used for the type adjective in the quantitative system, since the root "cecil" 
is already in use in the subrang cecilose (V. i 1 . i 2 . 2). 
BOVAL ALBANOSE. III. 8. 2. 2. 
Megascopic characters. Very dark gray, compact, aphyric, but sometimes with very rare 
phenocrysts of leucite and augite, aphanitic. Occasionally slightly mottled if not quite fresh. 
Microscopic characters. Holocrystalline, granular, partly poikilitic, leucite, augite, 
melilite, nephelite, olivine, anorthite, magnetite, apatite. 
Anorthite. About 4 per cent, 0.05 to o.iomm., subhedral, tabular, twinned. 
* Cordier, Description des Roches, Paris, 1868, p. 117. Cf. C. R. VIII Cong. Geol. Int., Paris, 1901, p. 1051 
Leucite. About 40 per cent, 0.05 to 0.20 mm., subhedral to anhedral, equant, round 
sections, clear, inclusions common, small, usually black, regularly arranged, skeleton forms not 
infrequent. 
Nephelite. About 7 per cent, anhedral, interstitial areas. 
