ART. 19. 



MORDENITE — EOSS AND SHANNON. 



rare thin fibers attached to heulandite crystals lining hollow flesh-red 

 masses of heulandite. The snow-white masses show on fracture 

 the texture of porcelain and are lusterless and exceedingly tough. 

 These, when ground for analysis were found to be pure with a very 

 finely felted fibrous structure. The mean index of refraction of the 

 analyzed material was 1.473. The analysis gave the following 

 results and ratios: 



Analysis (4) of small pebblelike masses of mordenite. 



Constituent. 



SiOs 



AI2O3 



CaO 



MgO 



K2O 



Na20 



H2O+110° C 

 HjO-llO" C 



Total. 



Ratios. 



1.099 0.122 X 9 1.00 X 9 



.116 .116 X 1 .95 X 1 

 .0491 



•Oil .133 X 1 1.09 X 1 

 !066| 



:280} -128 X 6 



1.05 X 6 



The four analyses of the Idaho material agree in giving the silica 

 ratio as 9 instead of 10 molecules and the water as 6. For con- 

 venience in comparing the silica content, the several analyses are 

 brought together and their average compared with the values cal- 

 culated to suit the two formulas (Na2,Ca)O.Al203.9Si02.6H20. and 

 (Na,,Ca)O.Al2O3.10SiO2.6H2O in the following table, a 1 : 1 ratio 

 between CaO and NajO being assumed in calculating the theoretical 

 compositions : 



Comparison of mordenite analyses with formula percentage values. 



This comparison indicates quite conclusively that the correct 

 formula for all of the several physical modifications of the Idaho 

 mordenite is (Ca,Na2)O.AlA-9Si02.6H20 which is identical with 

 the formula assigned to flokite and contains 1 molecule less of 

 silica and 1 molecule less of water than the accepted formula for 



