294 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1909. 
tively. Although such minute traces are present in both acid and 
basic rocks, yet it is undoubtedly more closely connected with those 
which are highly siliceous and alkalic. The minerals in which it 
forms an essential component, as spodumene, lepidolite, amblygonite, 
and some tourmalines, are most often met with in granites and peg- 
matites derived from granitic magmas. Unfortunately, the granites 
and pegmatites which carry lithium minerals most prominently do 
not appear to have been analyzed, but there is reason for the belief 
that they are sodic rather than potassic in general character. The 
very common association of lithium with soda rather than with potash 
in many minerals also points to the same conclusion. 
Beryllium is much like lithium in its associations, beryl and other 
rarer minerals which contain it occurring for the most: part in granites 
or pegmatites. Few analyses exist of such beryl-bearing rocks, and 
beryllia has seldom been estimated separately from alumina in rock 
analysis, but such data as are available and the common mineralogical 
association of beryllium and sodium point to the conclusion that the 
element is most at home in sodic magmas. 
Attention may be called to the fact that beryl, in spite of its com- 
mon occurrence, is not given in the list of descriptions of the rock- 
forming minerals, such as those in the standard works of Zirkel, 
Rosenbusch, and Iddings, though Lévy and Lacroix briefly described 
it in their work and it is placed on their large colored table of 
birefringences. In its optical properties it closely resembles nephelite 
and apatite, and being hexagonal in crystallization as well, might 
readily be mistaken for one of these minerals. I have noted the fact 
that analyses of nephelite-syenites and other highly sodic rocks fre- 
quently show a decided excess of alumina which can not be explained 
by the apparent mineralogical composition of the rock, and the sug- 
gestion is made that this is possibly due to the presence of beryl, the 
beryllia of which would appear as alumina in the course of analysis, 
unless special means were taken to separate the two. On the other 
hand, the excess of alumina may be real and due to the composition 
of the magia. . 
Strontium has been shown by the analyses of the United States 
Geological Survey to be widely distributed in the rocks of this 
country. I have found it almost invariably when looked for in many 
European rocks, and it is almost constantly present in those of 
Australia. But it seldom occurs in more than traces, and the evi- 
dence in regard to its distribution is as yet inconclusive, in spite of 
the many modern analyses in which it is now determined, chiefly 
because of the small amounts usually met with. It would appear 
to be most abundant in rocks somewhat high in lime and with mod- 
*Les Minéraux des Roches (Paris, 1888). 
