4 CONTENTS. 



Page. 

 CRYSTALLOGRAPHY OP PERBERITB PROM BOULDER COUNTY, COLO. Continued. 



Discussion of the prism zone 55 



Habit 56 



Combinations 60 



Twinning 62 



Description of measured crystals 65 



Form system of the wolframite group 69 



Critical study of forms 69 



Forms and coordinate angles 71 



Combinations observed on the wolframite group. 73 



Bibliography 74 



ILLUSTRATIONS. 



Page. 



PLATE I. A, Ferberite inclosing finely brecciated granite, from Rogers tract, 

 Nederland, Colo.; B, " Peanut ore," ferberite inclosing finely 

 brecciated pegmatite, from the Conger mine, Nederland, Colo. ... 10 

 II. Brecciated granite and pegmatite cemented by ferberite, from Town 



Lot mine, Nederland, Colo 11 



III. Brecciated ferberite vein, showing crystals formed since brecciation, 



from Conger mine, Nederland, Colo 12 



IV. A, Cut and polished crystal of brown ferberite from Winnebago 

 claim, near Rollinsville, Colo.; B, Brecciated ferberite vein from 



the Conger mine, Nederland, Colo 13 



V. Vug in a ferberite vein nearly filled by scheelite, the cavity then 



remaining being filled by quartz 14 



VI. A and B, Thin sections of ore showing hamlinite (?), from Eagle 



Rock mine, 8 miles west of Boulder, Colo 15 



VII. A, Wedge-shaped ferberite crystals from the Lone Tree mine, Neder- 

 land, Colo.; B, Wedge-shaped ferberite crystals from the Hoosier 



mine, Nederland, Colo 18 



VIII. A, Crystallized ferberite from the "Crow patent," Nederland, Colo.; 

 J5, Crystallized ferberite from the Georgia A. mine, Nederland, 



Colo 19 



IX. Crystallized ferberite with elongated rhombic crystal faces, from the 



Nugget mine, Gilpin County, Colo 20 



X. Crystallized ferberite with elongated rhombic crystal faces, from the 



Nugget mine, Gilpin County, Colo. : A, Edge view; B, Side view.. 21 

 XI. Ferberite with rhombic crystal faces, from the Nugget mine, Gilpin 



County, Colo 22 



XII. Very fine specimen of ferberite with rhombic crystal faces, from the 



Nugget mine, Gilpin County, Colo 23 



XIII. A, Section of hiibnerite from the Dragoon Mountains, Ariz., showing 



zonal structures; B, Photomicrograph of granite from the Whet- 

 stone Mountains, Ariz., showing wolframite with warty protuber- 

 ances of scheelite along its edges 30 



XIV. Section of wolframite from Irish Creek, Va., showing interstitial 



scheelite... 31 



