46 



COLORADO PEBBERITE AND THE WOLFRAMITE SERIES. 



A definite, measured difference in crystallographic constants be- 

 tween ferberite (FeWOJ and hiibnerite (MnO 4 ) is not shown by the 

 table just given. The average axial elements given by Goldschmidt 

 represent closely the angular values for the different members of the 

 wolframite group. These values are also close to those obtained on 

 the Colorado ferberite as shown below. 



Comparison of angles of ferberite from Colorado with the values given in Goldschmidt' s 



Tables. 



The axial elements given by Goldschmidt, namely, a :b:c = 0.8255: 

 1:0.8664, /? = 89 32', therefore best represent the constants for the 

 entire wolframite group. 



The data for the percentages of manganese given in the table on 

 page 45 have been taken from Dana. 1 Descloizeaux's measurements 

 were made on material from Vilate, near Chanteloube (Haute- 

 Vienne), France. An analysis of wolframite from Chanteloube shows 

 4.84 per cent MnO and 19.32 per cent FeO. Krenner's measurements 

 were made on crystals from Ehrenfriedersdorf , Saxony, and an analy- 

 sis of material from the same locality shows 4.96 per cent MnO and 

 19.16 per cent FeO. Seligmann's ferberite from Sierra Almagrera, 

 Spain, contains 3.15 per cent MnO and 19.95 per cent FeO, according 

 to Doelter. 2 Two confirmatory analyses of the Spanish ferberite 

 show 3.00 and 3.02 per cent MnO with high FeO. Hiibnerite from 

 Colorado 3 showed 21.93 per cent MnO and 2.91 per cent FeO. 

 "Megabasite" from Schlaggenwald contained 22.24 per .cent MnO 

 and 3.74 per cent FeO. 



FORMS AND ANGLES. 



A total of 32 forms were determined on the ferberite crystals from 

 Colorado. Of these 12 are new for the wolf ramite group. These 32 

 forms are given in the table below with the measured and cal- 

 culated coordinate angles. The new forms are marked with an 

 asterisk (*). 



1 Dana, E. S., System of mineralogy, 6th ed., p. 984, 1892. 



2 Zeitschr. Kryst. Min., vol. 11, p. 348, 1887. 



3 Penfield, S. L.; see Dana, E. S., op. cit., pp. 983, 984, 



