288 



Weidman and Zenker — Marignacite. 



the microscope inclusions of quartz and feldspar were seen. 

 This examination showed the mineral to be homogeneous, with 

 none of the characteristic features of alteration or of replace- 

 ment. 



Chemical Analysis. — -The pyrochlore used for analysis was 

 first picked out by hand from the crushed rock. As the latter 

 was somewhat disintegrated, many of the small octahedral crys- 

 tals were readily separated from the associated minerals by 

 crumbling the rock under pressure of the hand. Before the 

 mineral was powdered each crystal was examined with a hand 

 lens and all adhering minerals were rubbed off so far as pos- 

 sible. After being powdered and passed through a 100-mesh 

 sieve, the powdered material was subjected to separation by a 

 specific gravity solution of silver-thallium nitrate, and by this 

 method the adhering and included particles of quartz, feldspar 

 and acmite were separated from the pyrochlore. The rela- 

 tively high specific gravity of the pyrochlore furnished con- 

 ditions favorable for the separation by the specific gravity 

 method, and for this reason, as well as others later described, the 

 mineral analyzed is believed to have been essentially pure. 



The analysis of the pyrochlore made upon 3 - 15 grams, and 

 the molecular ratio of the constituents, is as follows : 



Analysis of Pyrochlore [Marignacite) from Wausau, Wiscon- 

 sin. 



Analysis 



Cb 2 5 55-22 



Ta 2 5 5-86 



Si0 2 ■_ 3-10 



Ti0 2 2-88 



Fe„0 3 '0-50 



FeO 0-02 



Ce 2 3 . 13-33 



Yt 2 3 5-07 



ThO„ 0-20 



CaO" 4-10 



MgO 0-16 



Na 2 2-52 



K 2 . 0-57 



F none 



H 2 OatllO°+ 5-95 



HO at 110°— 0-45 



99-93 



Molecular Ratio 

 •198 

 •013 

 •051 

 •036 

 •003 



040 

 022 

 001 

 073 

 004 

 041 

 006 



•331 



A1 2 3 , MnO, Sn0 2 , W0 3 , Di 2 0„ La 2 3 , Er 2 3 , occur in traces, 

 while F, Zr0 2 , BeO, U0 2 , Li 2 0, could not be detected. The 

 mineral shows no radio-activity. 



