PETROLOGICAL ABSTRACTS AND REVIEWS 8I 
best be described as hornblendite, passing into hornblende picrite in 
places, though differing from the normal types, which carry basic plagio- 
clase, in that in these rocks the general feldspar is perthitic orthoclase 
with some albite. The rocks are intermediate between the syenites 
with which they are associated and the kentallenites. The influence 
which the included quartz bowlders have had upon the magma is shown 
in the local concentration of the alkalies around them. In the magma, 
which is predominantly hornblendic, the quartz bowlders are replaced 
by alkali feldspars and quartz. Calcium feldspars, such as one would 
expect in a calcic magma, are entirely absent. 
The central acid phase of the intruded mass is quartz syenite, con- 
sisting of hornblende and less biotite in a matrix of feldspars, chiefly 
orthoclase with some albite, and quartz. 
The kentallenite occurs in a mass about fifty acres in extent at Balna- 
hard, and closely resembles the type rock from Kentallen Quarry. A 
porphyritic phase of this rock is also found. 
Augite diorite, in the sense used by Hill and Kynaston, forms the 
largest outcrop of igneous rocks on the island. It is a black-and-white 
rock with about equal amounts of femag and feldspathic constituents. 
Under the microscope the rock shows a porphyritic texture with biotite, 
pale-green augite, some hornblende, and some pseudomorphs after 
olivine in a groundmass of about equal amounts of perthitic orthoclase 
and plagioclase—oligoclase and oligoclase-albite. (Query: porphyritic 
augite monzonite ?) 
The minor intrusions on both islands consist of dikes and sheets, and 
are lamprophyres, basalts, and a few felsites. The lamprophyres are all 
vogesites and generally strike in an east-and-west direction. The north- 
west dikes are olivine “dolerites” and monchiquites, the former being 
fine-grained dark rocks, rarely porphyritic or vesicular, of perfect ophitic 
texture, and consist of olivine, some biotite, zonal feldspars of labradorite 
with oligoclase rims in some places, and purple augite. The rock is a 
typical olivine diabase as the term is used in America. A variety of 
this rock but containing a considerable amount of analcite and zeolites 
occurs and of this the authors say it “may be described as analcite- 
bearing dolerite.” To this rock the new name Crinanite is given. It 
is thus described: 
The crinanites, then, are dark-coloured, fine-grained basic rocks consist- 
ing mainly of olivine, augite, and plagioclase felspar, with a considerable amount 
of analcite and zeolites. Olivine is abundant in small grains more or less 
altered to serpentine. The augite is always purple and is sometimes bluish 
