272 Brush and Dana—the Spodumene of Branchville, Conn.., 
found scales of eens large too as compared with those in nor- 
mal cymatolite. 
4, Muscovite. 
As a distinct mineral, independent of its usual associate the 
albite, the potash-mica, muscovite, plays an unimportant part 
among the spodumene pseudomorphs at Branchville. It oc- 
curs very commonly in thin scales coating fracture-surfaces in 
the interior of the altered crystals. It is also found in small 
ohaer he of a light Dinaneed yellow color and has a greasy 
e occurrence of the mica yrith the albite, forming the 
cymatolite, has already been described under that head. The 
analyses of the cymatolite show that the mica has the formula 
of normal muscovite, viz: (K, H),A1,Si,0, Taking the ratio 
of K,0:H,O=1:8, corresponding approximately to analysis 2, 
the calculated composition of this muscovite is 
Sid, 46°23 
Al.Os 39°52 
K,0 9°35 
H,0 5°20 
00°00 
e complex cong of cymatolite having once been estab- 
lished, it is easy to many specimens in which the mica 
ary albite are so distinct that their inde- 
jj unaid se he occurrence of albite 
f pore separated from thealbite. Fig. 
| 20 shows a part of a section across a crys- 
tal, with the nucleus of spodumene (s), then 
£ spodumene (f), next cymatolite (c) grad- 
zi Tanne into pure and soft silvery mica (9), 
and finally a coating of albite (a). Such a 
ase shows the extent to which the segre- 
gation of the obiiteittiaite of the cymatolite can go on. 
the Massachusetts specimens, the mica, as an independent 
mineral, is, geet cae to Mr. Julien, much more abundant. 
We quote, on a following page, a remark of his on this point. 
