280 Brush and Dana—the Spodumene of Branchville, Conn., 
We are obliged to conclude that either the muscovite, if 
formed at the same time with the albite, has entirely disap- 
peared, or else that the method of formation of the albite was 
sometimes different from that previously explained. It ean 
hardly be questioned that in the cases mentioned it must have 
been formed independently of its associate, the muscovite. 
Where the albite has a distinct fibrous structure it must have 
been formed from the § spodumene (compare also figs. 8 and 
12). The albite was probably made from this by the action of 
a solution of sodium silicate changing the remaining lithium 
of the eucryptite to sodium and introducing two molecules of 
silica. It may also have been formed immediately from the 
spodumene, as expressed in the following equation : 
Li, Al,Si,O,2 + 2810 = Na, Al,SieQyo. 3 (4) 
Spodumene. Albite. 
Besides the albite poems ae there are also those con- 
ot ae microcline, which require ex- 
em, as has already been stated, 
case of the albite, taking into account the change of alkali, 
Li, Al,Si,0,4 + 28i0, = Ky AlSisQi¢ (5) 
umene. Microcline. 
There is no reason to think that the microcline was not formed 
1 o the segregation and simultaneous crystallization of the 
resulting minerals in large masses ins te mix- 
tur n connection with these it is interesting to call atten- 
es. 
tion again to the fact fap the masses of microcline in a single 
crystal, though often isolated and apparently quite independent, 
are yet in most cases in parallel position. This is a signifi- 
cant fact in its bearing upon the conditions of formation. 
These agglomeration pseudomorphs seem to be more abund- 
ant at the Massachusetts localities, *as described by Mr. Julien, 
