ANORTHOSITE-GABBRO IN NORTHERN NEW YORK 47 
of almost perfect mono-mineralic dikes. The pyroxenite dikes 
quite certainly, and the hornblendite dikes most probably, are of 
pegmatitic, magmatic origin, the magmatic solvent or solvents 
(probably largely water) having disappeared during the crystalli- 
zation. In conclusion it is suggested that mono-mineralic dikes 
like the pyroxenite and hornblendite above described should not 
necessarily, as Bowen" reasons, be excluded from the category 
of intrusive rocks. Is it not true that all active magmas are more 
or less rich in mineralizers, and is it not further an open question 
as to whether any magma can remain active, that is, still 
possess an intrusive power, after its mineralizers have all dis- 
appeared? Pegmatitic magmas of relatively early origin in 
their parent-rock are probably such powerful agents of intrusion 
and even of injection because of their richness in mineralizers. 
Does not the argument that no rock consisting of but one mineral 
could ever have existed as an intrusive magma, because at least 
one mineral must act as a solvent and another as a solute, dis- 
regard the perfectly plausible possibility of a single substance 
dissolved in some solvent which itself may not crystallize along 
with the dissolved material ? 
tN. L. Bowen, Jour. Geol., Vol. XXV (1917), pp. 218, 235-36, 242-43. 
