284 Brush and Dana—Spodumene and its Alteration. 
The phosphoric acid shows that a little parse: was present, 
and the corresponding amount of lime (1°86) should conse- 
quently be deducted. The analysis’ agrees reasonably we 
with the analyses of montmorillonite from Montmorillon, 
France. It is also closely related to a similar clay described by 
Helmhacker, from Macskamezé, Transylvania.* 
It has been stated that this mineral was, as first found, very 
moist ad coherent. It seemed a matter of some interest to 
desiccator over —— acid. Repeated weighings ct _ 
it continued to lose weight gradually for a period of s 
seven weeks, the “ai soothe then 9°80 p. c. The total loss ake 
ignition was about 17 
The exact cri of Abie montmorillonite to the spodu- 
mene ea py cannot be given. The fact that it occurs 
so intimately with the spodumene, and too with the cymatolite, 
seems to imply that it owes its origin to the former. It be- 
longs, however, to a later part of the process, for it is almost 
nena free from alkalies) The suggestion that it may have 
made from feldspar and thus have afforded the alkalies 
a ee in the alteration of the spodumene would seem at 
first sight plausible. But in the frst place the feldspar of the 
vein with which it occurs is entirely fresh and unaltered, and 
then, as far as our cetot ties have yet gone, the quantity is 
much too small. It would rather seem to be a local result of 
the further alteration of the lastueiboleta We do not feel able 
at present, however, to speak with decision about it. 
In concluding our maar we would express our acknowl- 
cringe to Mr. Penfield, and to Messrs. Wells and Dewey, to 
om we are indebted for the analyses here published. 
DESCRIPTION OF PLATE. 
n the figures the pieigein por have the following signification :—a = albite 
spa here it is to be remembered box (as haba earlier) most of the albite 
contains scales of ntfatdhecreg and hen + es into cymatolite; c = cymatolite ; 
oni clin - 
a, 1b, ions Te a single “erysta tal, 15 inches wide and 43 a 
at intervals of about 5 inches. la, from r the terminated extremity, consist 
priucipally of 8 —— ( s with eymatolite O along the pgrt co a little 
glassy spodumene (s) 0 side. hows only 8 ene and 
pan a the latter spracite cas my el ea og Pare in la. ‘si ror the lower 
extremity of the crystal shows yang only. 
2. Section across a crystal, 44 inches wide, now entirely altered to cymatolite. 
The intricate wavy structure of this sree is shown, as also the tendency of the 
fibers to be at right angles to the edge 
3. Partial section taken longitudinally the central portion consists of finely 
granular albite (a), with lines of coarsely granular, and cleavable, microcline rac 
the exterior is cymatolite (c). 
* Tschermak. Min. u. Petro. Mitth. 1879, p. 251. 
