JOURNAL 
OF THE 
WASHINGTON ACADEMY OF SCIENCES 
Vou. 13 JANuARY 4, 1923 No.1 
PETROLOGY.—The genesis of melilite1 N. L. Bowrn, Geophysical 
Laboratory, Carnegie Institution of Washington. 
In a recent paper the writer described some alnoitic rocks from 
Isle Cadieux, Quebec, that contain the mineral, monticellite. This 
was presumed to be the first recognition of monticellite as an igneous- 
rock mineral.2. After the paper was published K. H. Scheumann 
called my attention to a mineral occurring in rocks of a related char- 
acter from Polzen, Bohemia, of which mineral he has said: ‘‘ Perhaps 
we are dealing with monticellite, whose occurrence in a rock so rich 
in magnesia would not be surprising, or perhaps with an olivine rich 
in the monticellite molecule.’”’ Scheumann’s descriptions show that 
the mineral is, with little possible doubt, the same as that in the 
Canadian rocks and is to be regarded as monticellite even though 
his optical determinations were not sufficiently quantitative to 
establish its identity.? These observations of Scheumann’s were 
not known to me nor were they recalled by any of the petrologists 
with whom I discussed the occurrence of monticellite in igneous rocks. 
Had the Polzen rocks been described under more familiar names such 
as alnoite, melilite basalt, with such qualifying terms as may have 
been necessary, they and their characters would not have escaped 
my notice in general abstract literature, but appearing under the 
disguise of locality names it is perhups not surprising that they did 
not attract attention. Of this matter more later. 
In the paper on the Cadieux rocks were included the results of some 
experimental work designed to throw light on the origin of some of 
the mineral phases present. Experiment showed that, in certain 
1 Received December 7, 1922. 
2.N.L. Bowen, Am. J. Sci. III: 1-34. 1922. 
3K. H. Scheumann. Konig]. siischs Gesell. d. Wiss. Abhandl. 32: 7,732. 1913. 
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