Schaller and Hillebrand — Chemical Notes on Lawsonite. 197 









Mol. Eatio 



Calc. for ths formula 

 H 4 CaAl 2 Si 2 O 10 



SiO, . 



Ti0 2 



AlO, 





38-45 



0*38 

 31-35 1 



0-86 \ 



o-io 1 



trace 

 17*52 ' 



0-17 [ 



0'23 



0-06 J 

 11-21 



1-98 

 097 



1-00 

 1-95 



38-34 



2 3 



Fe 2 3 



FeO.. 



MnO 



CaO . 



MgO 



KO. 



faint 



32-44 

 17-80 



2 



Na,0 

 H s O 



(ignition) 



11-42 



100-33 100-00 



Titanium is not considered in the ratio because probably 

 present as an inclusion of rutile or titanite. If the latter, the 

 ratio would perhaps approximate still more closely to the theo- 

 retical than it does. The agreement with the formula deduced 

 by Ransome and Palache from their rather widely differing 

 analyses is very satisfactory. The behavior of the mineral 

 before the blowpipe is somewhat different from that given by 

 those authors, or rather their statement needs amplification. 

 On first applying the flame, a splinter appears to fuse easily as 

 stated, and there is formed a blebby glass, or on larger splinters 

 a porous sinter, but this fusing is only momentary, and it 

 requires the highest heat attainable, under which the fragment 

 emits quite an intense light, to produce a further softening and 

 rounding of the edges. If a rather large splinter is held in the 

 flame of the blowpipe, or in a small flame of a blast lamp, a very 

 sudden and marked exfoliation is observed, but even the extruded 

 points and edges do not fuse completely in the highest attain- 

 able heat. The semi-fused surface, however, appears on cool- 

 ing dark and sometimes nearly black where the heat was most 

 intense. If care is taken, in producing this exfoliation, to 

 apply the flame but for a moment, it has been noticed that a 

 singularly shaped excrescence may shoot out from a point of 

 the surface. 



Laboratory of the U. S. Geological Survey, November. 



