JAN. 4, 1923 BOWEN: THE GENESIS OF MELILITE 3 
with other minerals.’’* It is believed that the melilite was formed as 
a result of this attack though, admittedly, it does not occur in typical 
reaction-rim form. 
The other melilite rock showing analcite is a melilite-nephelite 
basalt from pipe No. 3 E 5°S of Wolf Kraal House, Namaqualand.’ 
It shows nephelite and analcite in the same relation as that described 
above, but the whole rock is much finer-grained than the Hawaiian 
example and the general relations of the minerals more obscure. 
It is apparent, then, that analcite does occur as a residual mineral 
in some melilite rocks. In deep-seated rocks the reaction between 
nephelite and pyroxene to produce analcite and melilite is reversed. 
It is probable that some melilite is produced by the addition of lime 
to ordinary basalts, but when so formed one would expect it to be 
found in deep-seated rocks as commonly as in effusive and dike rocks. 
The fact that melilite is practically absent from deep-seated rocks 
suggests the dominance of the other method of production, namely, 
interaction of nephelite and pyroxene which requires the rapid 
cooling accompanying eruption in order to prevent its reversal at 
lower temperatures. 
ROCK NAMES 
It has been noted on a former page that polzenite and its characters 
escaped notice on account of its unfamiliar name, nevertheless it should 
be stated that polzenite is as much entitled to a new and distinctive 
name as many other rock types. It does seem, however, that the 
time has come to call a halt to the wholesale manufacture of rock 
names. Frequently these names designate only a slight departure 
in texture or in relative proportions of minerals from some common 
types with familiar names, and these variants could more profitably be 
described under the familiar names with appropriate modifying words or 
phrases. Such a procedure would undoubtedly result in many cumber- 
some names, but better a cumbersome name that immediately conveys 
the character of the rock to thereaderthan aconcise name that conveys 
nothing but the locality where the rock happened to be first found. 
Lest it be supposed that the objections raised are directed principally 
against the polzenite of Scheumann, I wish to cite an instance nearer 
home. I have just read in manuscript a paper on Hawaiian lavas 
by my colleague Doctor Washington, in which paper the names 
kohalaite, mugearite, and hawaiite are used to designate certain 
Cross. op. cit.: p.21. 
* Locality so described by A. W. Rogers on submitting specimen to H. S. Washington 
for analysis. 
