and the Results of its Alteration. 261 
mene had all the appearance of passing insensibly into it; a 
i e obtai a p 
No, 2, G.==2°644. ; Il. Mean. atio 
SiO. 61:4 61°57 61°51 1°025 4 
Al,O; not determined 26°56 26°56 258 1 
Li,O 3°5 3° 3°50 “Hit : 
Na,.O 8°15 8°13 8°14 131 *249 0-97 
“Keo 0°15 0°15 0°15 001 
Ignition 0°29 0°29 0-29 
10014. 00°15 
The third portion was part of a smaller and well developed 
crystal, having the external prismatic form complete. It con- 
sisted in the interior of spodumene, then the B a aaa 
making up the greater part of the whole, and finall 
crust of cymatolite. The specimen analyzed was, as far as the 
eye could detect, perfectly pure and homogeneous. The color 
was greenish-white and it was decidedly translucent. The 
analysis afforded :— 
No. 3, G.—=2°649. , Tl. Mean Ratio. 
SiO, 61°78 61°64 61°71 1028 44 
Al.O;3 26°57 26°69 26°63 259 #1 
Li,O0 3°83 3°83 128 t eel y 
Na,O 8-16 8-16 132 
2 tr 
Ignition 0-21 0-21 
10053 10054 
If the mean analyses of the three groups be compared, it will 
be found that they agree very closely with one another; in 
fact the agreement is as close as could be expected for three 
successive analyses made upon the same material. But, as 
will be seen from what has already been said, the three samples 
were entirely independent, being taken from different parts of 
the ledge and differing in manner of association; the agree- 
ment between them thus becomes very striking. The ratio 
obtained for eac 
R,O: RyOy: SiO, = 1:1:4 
is the same as that of spodumene, from which it differs only in 
this: that one-half of the lithium has been removed and its 
ree (chemical equivalent) taken by sodium. The formula is 
then :— ° 
(Li, Na): Al.Si,O.2 = LigAlSi,Oi2 + NacAleSisOr2 (1) 
or = Li, Al,Si,Os + NazAlpSisOi¢ (2) 
It is shown below that the formula given in (2) is the correct one. 
he facts stated thus far would seem to be sufficient to prove 
that the mineral was homogeneous and had a definite composi- 
