Oenth and Penfield — Contributions to Mineralogy. 189 

 I II 







a 



b 

 Less 



a 



b 

 Less 



Impurities .. 



5-11 



impurities 



4'22 



impurities 



[Ignition, 



9-18] 











H„0. 





2-02 



2-11 



2-33 



2*43 



co 2 





7-16 



7-47 



6-85 



7-14 



CuO 





0-31 



0-32 



0-32 



0-33 



PbO 





4-S3 



5-04 



4-63 



4-82 



B10 3 





80-13 



83-64 



80-41 



83-81 



ZnO 





0-86 



0-90 



0-86 



0-89 



so 3 . 





0-50 



0-52 



0-56 



• 0-58 



100-92 100-00 100-18 100*00 



The lead is probably present as PbC0 3 and PbS0 4 , the cop- 

 per as malachite, the zinc as ZnC0 3 and the bismuth as 

 hydrated-carbonate, but the material is too impure to attempt 

 the construction of a formula. 



4. Natrolite. 



Associated with aegirite, eudialyte, titanite, etc., natrolite 

 occurs at Magnet Cove, Ark., in large colorless, cleavable 

 masses, the individuals being about 50 mm in length and h'^^ 

 broad. The cleavage, although apparently perfect, does not 

 yield good surfaces for reflecting light. The angle between 

 the cleavages is very near 90°, but most of the measurements 

 which were made are near 91° and 89°. The crystals are 

 colorless, some portions, however, are more or less opaque. It 

 was found that the latter contain a minute quantity of. lime, 

 while the colorless portion is free from it. The spec, gravity 

 was found to be 2-243. The analysis gave : 



H 2 9-81 



Si0 2 47-97 



A1 2 3 26-51 



NaO 1598 



100-27 



Chemical Laboratory, 111 S. 10th St., 

 Philadelphia, October 25th, 1891. 



