136 Cross and Hill. hnnnJ — M '.,.,, r<ils in the basalt of 



Aside from the H 2 0, these ratios agree closely with the theo- 

 retical requirements of laumontite 1:3:8:4, especially as it 

 can scarcely be suppoa al was absolutely pure. 



It is quite probable that a small amount of stilbite was in- 

 cluded with b, which would explain the high percentage of 

 Si0 2 . 



In regard to the amount of water found it is only necessary 

 to suppose that the dull particles have lost a part of their 

 v ater. v bile the inn -i>. tvi t grains are entirely fresh, in order 

 to explain the relation of water to the other constituents as 

 shown in the above ratios, a supposition in full accord with 

 the characteristic tendency of laumontite to lose its water on 

 exposure. 



The mineral is not quite so easily fusible before the blow- 

 pipe as typical laumontite should be, according to the text- 

 books, but the difference is not sufficiently pronounced to be 

 considered abnormal. 



Turning now to the more compact reddish-yellow deposits, 

 which correspond so closely to the one described, the same 

 constituent minerals were sought for. Some small cracks or 

 ftssares, ae --. were no- 



ticed, some of which were only partially filled with minute 

 white crystals. On splitting the mass open, along such a half- 

 filled crack, two surfaces were obtained, coated with minute, 

 but exceedingly perfect clear crystals. < asil; nvngnizable under 

 the microscope, as laumontite and stilbite. The little crystals 

 of the former show occasionally the clinopinacoid, and a steep 

 positive orthodome in ad< and basis. 



The sand obtained by simple fracture of the yellow, massive 

 portion, on being placed under the microscope, is seen to con- 

 sist largely of fragments of tabular crystals, the angles of 

 which, so far as tb» . correspond to stilbite. 



The grains which are not evident fragments of tablets, are in 

 part roughly prismatic, though seldom showing definite faces ; 

 neither could the opt; torily determined. 



Chemical analyses were made from two different specimens 

 of the yellow granular mass, care being taken to exclude all 

 jvddish'spherules. The re.-ults arc L'ivcn under c and d below. 



