346 BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



undertake to give accurate scientific identifications of zeolites from 

 near Salmon. The Museum replied in the affirmative, but no 

 specimens were received and letters addressed to Mr. Albee were 

 returned. No zeolite specimens from this locality have been seen, 



PTILOLITE (436) 



Hydrous calcium-sodium-potassium alu- 

 minium silicate (Ca,K2,Na2)O.Al 2 03. 

 10SiO 2 .5H 2 O. Orthorhombic. 



CUSTER COUNTY 



Ptilolite has been reported to occur at Challis in Custer County 

 by Koch. 08 Later investigations on better material have resulted 

 in the classification of this material as mordenite as fully discussed 

 below. True ptilolite is not known to occur in the State. 



MORDENITE (437) 



Calcium-sodium aluminium hydrous sili- 

 cate (Ca,Na 2 )O.Al 2 03.9Si0 2 .6H 2 0. Monoclinic. 



The fine cottony zeolitic mineral originally described as ptilolite 

 from near Challis in Custer County as mentioned above has since 

 been shown to be mordenite. A detailed study of this mineral, which 

 has previously been published with descriptions of the associated 

 minerals, 69 as in the main repeated below. 



CUSTER COUNTY 



The original specimen of the mineral from Challis was sent to the 

 United States National Museum for identification by Milton A. 

 Brown, of Challis, who thought it might be asbestos. A large box 

 of specimens of the minerals from the locality was later received from 

 Dr. C. L. Kirtley, of Challis. The mineral probably occurs in a lava 

 flow interbedded with Miocene lake sediments south of Challis. 

 Associated with the mordenite are heulandite, analcite, argentine 

 calcite, quartz, chalcedony, and chlorites, all of which are described 

 elsewhere in this report. The identification of the mineral as mor- 

 denite is the result of a careful study of the minerals of the group by 

 Dr. Waldemar T. Schaller, who has concluded that mordenite and 

 flokite are identical, but that the material from Wyoming which has 

 been called mordenite is a distinct mineral (clinoptilolite) and both 

 mordenite and clinoptilolite are distinct from ptilolite. 



The mordenite seems to be present in greater abundance and in 

 better specimens at the Idaho locality than at any other known 

 locality for the mineral. In the lot examined it ranges from fine 

 cottony felted aggregates through radial fibrous masses to dense 



68 Louis A. Koch. Amer. Mineralogist, vol. 2, p. 143, 1917. 



ro Mordenite and associated minerals from near Challis, Custer County, Idaho. Clarence S. Ross and 

 Earl V. Shannon. Proc. U. S. Nat. Mus., vol. 64, art. 19, 1924. 



