Table Mountain, near Golden, Colorado. 457 
of thomsonite contained very small, irregularly rounded parti- 
cles, imbedded in the outer surfaces. These particles which 
are clear, or slightly yellowish, do not affect polarized light 
sybase ly, and are not crystalline in form. ey are present 
koe regates. 
Analysis [IV was made from material taken from the purest 
and finest specimen of thomsonite as yet obtained. Here the 
a of thomsonite was unusually thick, and the separation 
om the underlying thin layer of chabazite was complete. 
The particles above referred to were present in very small 
quantity in the upper part of the blades, and even if they con- 
sisted of pure silica could have affected the result but slightly. 
While believing that the results obtained indicate a greater 
variation in the composition of thomsonite, than is allowable 
under the generally accepted formula of Rammelsberg, 
m (2CaAlSi,O, + 5aq.) 
n (2Na,AISi,O, +5aq.) 
the further discussion of the question is reserved for the final 
repor 
It was found that a varying quantity of water (usuall 
about 2 per cent) could o a be driven off at a very hi h 
temperature, b yet, no simple molecular ratio between 
this water and the compound has been fo T aterial 
was dried at 100 The action of this thomsonite before the 
blowpipe is entirely normal. 
e thomsonite of Table Mountain was first identified, 
through a quantitative analysis, by Carlton Hand, at the 
time a student, now, assistant in assaying, in the School of 
Mines, at Golden. The analysis was never sistsliaiea and has 
since been lost 
3. Analcite, 
Analcite follows thomsonite in time of deposition. At the 
locality mentioned on North Table Mountain, its crystals are 
pure white or transparent, and vary in size from very small 
ones, to those nearly an inch in diameter. The predominating 
form is the common Geko by 4 % 2 Or teccpe its octa- 
appearance of 
3 is very characteristic of the Ta hie Yate analcite, though 
the form is — r prominent, and is nuee a by an 
exceedingly narrow line. According to Zirkel,t the form $ 
has been scare os "but once on analcite, viz: by Laspeyres on 
that from the Kerguelen islands, 
*.C. Rammelsberg, Mineral Chemie, 1875, p. 657, 
¢ Macmane: -Zirkel, ‘‘ Elemente der Min neralogie. ” Leipzig, 1881. 
