322 
DE. JOHN S. FLETT: PETROGKAPHICAL NOTES ON THE PRODUCTS OF 
augite and sphene; in others lime-felspar is common, while a few contain small 
rounded grains of quartz. The absence of hornblende, garnet, vesuvianite, and 
epidote is rather striking. 
The wollastonite, which is the most important mineral, forms plates, fibres, and 
irregular blades. Sometimes it shows traces of idiomorphism, being elongated parallel 
to the b axis. Very often its fibres are sub-radiate, or have a tendency to spherulitic 
or stellate groupings. The augite is dark green, sometimes brownish green, and forms 
only small grains which rarely exhibit crystalline faces. The felspar, also, is anhedral 
as a rule. It shows albite twinning, more rarely Carlsbad and pericline twinning, and 
belongs to the basic end of the plagioclase series, being near anorthite in composition. 
Quartz is rare and occurs only as rounded grains. Granular sphene is always present, 
but never well crystallised. 
The green veins which traverse these rocks are mainly augite ; the white patches 
consist of wollastonite and felspar, but the rocks show little uniformity in structure 
or in the shape and size of their component minerals. 
Where anorthite is abundant it has a tendency to idiomorphism, and its crystals 
are frequently bounded in part by good crystalline faces (Plate 27, fig. 4). The matrix 
is then wollastonite, augite, and smaller grains of felspar. The large felspars enclose 
wollastonite, augite. and the other minerals of the rock. The porphyritic crystals 
give rise to a structure somewhat resembling those of igneous rocks. Professor Lacroix 
has noted the same phenomenon in the calc-silicate hornfelses of St. Vincent. 
Quartzites , Baked Sandstones .—We obtained also a few fine-grained contact-altered 
rocks consisting mainly of quartz. They may have been sandstones or siliceous 
portions of the underlying sedimentary beds, or perhaps secondary deposits of quartz 
among the igneous rocks. 
Albite Rock .—The most peculiar of these rocks is a small pale-coloured fragment 
which proved in microscopic section to consist of albite and pleochroic green augite 
(segirine augite). In the calc-silicate hornfelses the pyroxene sometimes has a weak 
pleochroism ; in the granular augite of this rock it is quite strong and ranges from 
yellow to dark green. The albite forms long prisms, not perfectly idiomorphic, but 
with irregular or indented edges. A little quartz occurs among the felspars. There 
are no phenocrysts. The origin of this rock is obscure ; it is unique in our collections, 
and no similar ejecta' have been found in Martinique. As its pyroxene resembles that 
of some of the calc-silicate hornfelses, we have placed it with them. 
The Older Igneous Rocks of St. Vincent. 
Our collections do not include a large number of specimens of the older igneous 
rocks of St. Vincent, but they have been supplemented by a series which 
Professor Lacroix sent us, and these enable us to show what are the main 
petrographical features of the island. Professor Bergeat has grouped the rocks which 
