THE NAMING OF ROCKS 691 
it is so abundant and important as to require a name to enter 
rock nomenclature, the geographical name may be used simply 
as a qualifier, as, Duluth olivine-gabbro. This usage gives the 
most exact discrimination without cumbering nomenclature with 
a multitude of independent names. In any of the foregoing 
classes of names the prefixes meta, apo, epi, schisto, gneisso, 
or other terms may be inserted for the altered rocks.* 
Under the plan proposed we shall have coérdinate simple 
names of about the value which Rosenbusch has designated as 
family for rocks which are the most abundant and important. 
We shall have compound names for rocks intermediate between 
the more abundant kinds. We shall have names with geological 
qualifiers, either compounded: or not, as the case demands, for a 
further refinement in discrimination. In any of these three 
classes of names mineralogical qualifiers may be introduced as 
an additional discrimination. For all of the previous classes we 
shall have prefixes, with definite meanings, for the altered equiva- 
lents of the diiterent rocks. 
The method proposed is practically that of a binomial or tri- 
nomial nomenclature. The fundamental names would be based 
primarily upon abundance, and secondarily upon other factors. 
The secondary names would be introduced under the same prin- 
ciples. 
Application of plan proposed.— How this plan can be worked 
out may be illustrated by some cases from recently described 
rocks. (1) Mordmarkite,? by Washington, is placed as equivalent 
to mica-hornblende-quartz-syenite. The rock is therefore a syenite. 
Assuming that this rock is sufficiently abundant so that it should 
have a place in nomenclature, it may be called nordmarko-syenite. 
In the same way, akerite3 (augitic quartz-syenite) may be called 
«In another place (Metamorphism, Monograph, U.S. Geol. Surv.) I shall discuss 
in detail the use of these terms. But in the present paper I do not wish to take up 
the subject. Here I wish merely to suggest a method of handling the altered rocks, 
rather than to discuss the details of its application. 
?The petrographic province of Essex county, by H. 5S. WASHINGTON : JouR. 
GEOL., Vol. VI, 1898, p. 799. 
3Jour. GEOL., Vol. VI, p. 796. 
