and the Results of its Alteration. 269 
A considerable number of sections of cymatolite, both in its 
purest normal varieties, and in its transition forms from # spod- 
umene on the one hand and to albite on the other, were exam- 
ined. The result not only proved the fact of the mixture of 
muscovite and albite, but also gave the explanation for the 
remarkable uniformity of the analyses, for in most cases the 
mixture is in the highest degree intimate. A section of cyma- 
tolite like that represented in fig. 1c (Plate), when examined in 
polarized light, is found to consist of long, slender, somewhat 
curved fibers, giving very brilliant colors and showing the 
characteristic structure of mica, and between them grayish 
portions of albite. In some cases the fibers of mica are so 
—— All the details of the structure came out most 
clearly in the sections in polarized light. The feather-like 
them becoming more and more distinct as their distance 
e 
any details could be added, but enough has been said to 
make the character of the observations apparent on which the 
statement as to the compound nature of cymatolite is based. 
The mica and albite are always distinct from one another. In 
some cases they both appear in larger masses having segrega- 
ted together in the process of alteration. More is said about 
this later. 
The only foreign mineral observed in the slides was one 
which occurs in hexagonal prisms, and can hardly be anything 
but apatite, as it agrees optically and crystallographically with 
that species. It is seen scattered through the cymatolite some- 
times rather abundantly, occasionally also in the 8 spodumene, 
it is, however, not for a moment to be confounded with eucryp- 
