1892.] Mineralogy and Petrography. 697 
observed on them are æ% P, œ» PX%, œ Pæ, oP, P, and 4P. In the 
neighborhood of ore veins the mineral is changed into pinite. 
A Melilite Rock from North America.—From the bed of the 
Ottawa River, near Ste. Anne, not far from Montreal, Can., Mr. Adams* 
has obtained the first melilite rock described from North America, It 
occurs as a dyke in Potsdam conglomerate. The rock, which has a 
fine-grained, dark groundmass, often contains phenocrysts of green and 
red olivine, biotite and pyroxene. The matrix in which these lie con- 
sists of small biotites, olivines and pyroxenes, between which lies a 
still finer aggregate of melilite, pyroxene needles and a small quantity 
of a colorless mineral that may be nepheline. Perofskite, apatite and 
magnetite are also present in it. The brown biotite is an anomite, with 
a small biaxial angle. It consists of an interior inclusion-free nucleus, 
usually with a rounded outline, surrounded by a zone filled with augite 
microlites and bounded by crystal faces. The olivine contains but 
little iron (12.65%). The red color of some grains is due to inelu- 
sions of iron oxide. Its alteration is sometimes into serpentine, but 
more frequently into ferriferous magnesite and breunerite, whose 
composition is Mg CO, = 64.83; Fe CO, = 26.16; Ca CO, = 1.66; 
impurities = 7.35. The alteration begins along cleavage cracks and 
proceeds inward from the peripheries of the olivine grains. The pyrox- 
ene phenocrysts are colorless and have an extinction of 42°. Like 
the biotite the augite grains are also bordered by a zone of alight brown 
color, which is of the same substance as that of the smaller phenocrysts 
and of the needles in the groundmass. The extinction in the zone is 
often 16° greater than that of the nucleus. The characteristic mineral 
of the rock, the melilite, possesses the peg structure and all the other 
peculiarities of this component of the Alnö specimens. Basal sec- 
tions have rectangular or octagonal outlines, while prismatic sections 
are often flattened parallel to oP. The rock differs from the type alno- 
ite in possessing no feldspar. The author thinks it is connected in some 
way with the Montreal volcanic center, forming Mt. Royal, which, as is 
well known, consists largely of eleolite syenites and related rocks. 
The composition of the rock follows : 
SiO, TiO, AlO, FeO, FeO CaO MgO K,O Na,O Co, H,O 
35.91 .23 11.51 2.35 5.38 13.57 17.54 2.87 1.75 9.40 
The Sanidinite Bombs of Menet and Monac.—The sani- 
dinite bombs included in the trachytes of Menet, Cantal and of Monac, 
‘Amer. Jour. Sci., April, 1892, p. 269. 
