116 GEOLOGICAL AND MINERALOGICAL NOTES. 



composecl of feldsp.'irs and feebly poLirizing nepheline in 

 a iietirly complete felting of aegirine crystals and grains, 

 some of which sink to the finest diist. These segirine 

 grains are so abundant in the feldspars of the ground-mass 

 that the specific gravity of the feldspar in the rock pow- 

 der, even after passing through the 100 sieve, could not 

 be clearly made out, bnt with tlie inchisions of segirhie it 

 was as low as 2.59. This rock povvder gelatinized readily 

 with acid and, lipon evaporation, an abundance of gypsum 

 crystals appeared, thus characterizing some of the minerala 

 in the ground-mass as belonging to the hauyne group. In 

 a communication received at a late date (June 17), from 

 Prof. H. Rosenbusch, in relation to this rock he says : 

 "Specimen No. 4 is a very good representation of the dyke 

 rocks which I have called linguaite. Phenocrysts of 

 orthoclase in scarce quantity are disseminated in a holo- 

 crystalline mass of feldspar, nepheline and augite. I feel 

 very sure there may be some hicite in it, bat I did not 

 succeed in proving it until to-day." The letter is dated 

 June 6, 1893. With this determination the phonolite dyke 

 rock would, therefore, be a lucite-tinguaite. 



The microscopical structure of the typical augite-syenite 

 from various outcrops is as follovvs : — Thin sections pre- 

 pared from specimens collected in an old quarry on the W. 

 D. Pickman estateat Beverly Cove ;numerouslargeporphy- 

 ritic crystals of microcline-microperthite,^ some multiple 

 twinnedplagioclase, probably labradorite, much orthoclase, 

 augite in two forms, one in large ragged crystals, and the 

 other in long needle-shaped crystals enclosed in the feld- 

 spars as microliths, numerous small ragged crystals of 

 segirine, some brown hornblende, red biotite in large 



1 This form of feldspar is cliaracteristic of Professor Brögger's microline-mi- 

 croperthite in the uugite-syenite rocka of Norway.— Biögger, Min. der Syenite Py., 

 p. G27. 



