F. W. Clarke — Minerals of Litchfield, Maine. 267 



"The small grains of the other secondary mineral are so 

 intermingled with the uniaxial zeolite as to indicate that both 

 are derived from the sodalite. They are easily distinguished 

 from the zeolite in which they are imbedded. In transmitted 

 light they are perfectly clear and transparent, with so high an 

 index of refraction as to appear to rise above the surrounding 

 mass. The grains are entirely without crystallographic bound- 

 aries, but are traversed by distinct cleavage lines. Between 

 crossed nicols they are much more brilliantly colored than the 

 associated zeolite, and if the section is rotated they become 

 dark when the cleavage lines make a prominent angle (15°-33°) 

 with the principal sections of the prisms. The mineral is cer- 

 tainly biaxial, and in all probability belongs to one of the two 

 inclined systems of crystallization, but its definite determina- 

 tion is not practicable under the circumstances." 



In view of the presence of an impurity in the new zeolite, 

 Mr. Diller suggested a re-analysis of it, to be made on carefully 

 purified material. The purification, by means of Sonstaclt's 

 solution, he kindly undertook, determining at the same time 

 the specific gravity of the mineral. The crude material gave 

 him a sp. gr. of 2'263, while the zeolite was a little lighter and 

 the imbedded grains a little heavier. After purification the 

 coarsel} 7 powdered zeolite was carefully picked over under the 

 microscope until Mr. Diller felt confident that the sum of all 

 impurities could not exceed one per cent. The mineral, then 

 dried at 100°, gave me the following analytical results : 



H 2 . 12-98 



Si0 2 38-99 



A1 2 3 33-62 



CaO -07 



Na 2 13-07 



KO 1-12 



99-85 

 These figures confirm the previous analyses, and show that the 

 impurity which vitiated them must have been small in amount 

 and similar in composition to the new zeolite. The latter, I 

 think, may be considered as fairly well established; and its 

 formula may be written A] 3 (Si0 4 ) 3 lSfa !! H . 3EI 2 ; which requires, 

 water, 13-76; soda, 13-54; alumina, 3341, and silica, 39*29. 

 This composition, and the manifest relations of the mineral to 

 nephelite, the parent member of the group, naturally suggest 

 for it the name hydronephelite, which seems to be both appro- 

 priate and descriptive. Chemically, as I have already ob- 

 served, the species approximates to a soda thomsonite; but 

 optically it appears to be quite different. This fact suggests 

 the desirability of a careful microscopic re-examination of all 



