July, 1889. 
A GRANITE CONTAINING LITHIA. 
157 
of the triclinic felspar makes the latter suggestion the more 
likely, or rather there does not seem enough felspar which 
has not the multiple twinning to account for the amount of 
potash present. On separating the constituents as accurately 
as possible by means of Sonstadt’s solution, I could get no 
satisfactory distinction between the various fractions within 
the limits of the specific gravities of the felspars. A great 
many grains, tested by Szabo’s flame reactions, showed the 
preponderance of soda in the felspar, but not such an absence 
of potash or such a fusibility as would have been expected in 
the case of albite; and in a few of the cases where the 
extinction angles could be satisfactorily determined the 
occurrence of angles of about 40° between the extinctions of 
the two sets of twin lamelke makes it more probable that at 
any rate some of the felspar is oligoclase. Still there 
was apparently another maximum extinction at about 30°— 
32° which would best suit albite, and the amount of lime 
compared with the soda, even allowing that some of this was 
contained in the mica, seems too low to allow of oligoclase 
being the chief basic felspar. 
In a paper on the Litliia Micas of New England, by 
F. W. Clarke, in the Bulletin of the U.S. Geol. Survey, 
abstracted in the Chemical News, June 3, 1887, the author 
speaks of the chief localities as situated along a belt of albite 
granite, and furnishing in almost all cases tourmaline of 
green and pink colours as an accompanying mineral. 
The quartz is chiefly noticeable on account of the very 
few so-called fluid cavities contained in it. Inclusions are 
common, but they are either flakes and needles of some 
mineral or minerals which I have not been able to identifv, 
or else ill-defined cloudy masses giving a rather dirty appear¬ 
ance to the quartz. These also occur in the felspar, and in 
both cases are often heaped in the central parts of a gram, 
or are gathered into zones, following more or less closely the 
outline of the grain. In among the larger constituents is 
found in some parts, indeed pretty generally, a rather 
irregularly intergrown micropegmatite, or sometimes it has 
more the look of the finely interlocked grains of quartz 
which are so common in some of the schistose rocks. 
The mica occurs in pearly-white flakes ; those which form 
part of the mass of the rock very often show but slight 
cleavage, and have a very slightly pink colour. Fragments 
held in the flame of the Bunsen burner give the intense 
carmine colour due to litliia, and it is in this mineral only 
that the alkali occurs, the felspar, so far as I have seen, giving 
no trace of it. 
