184 Genth and Penfield — Contributions to Mineralogy. 



Art. XXII. — Contributions to Mineralogy, No. 52; by F. 

 A. Genth. With Crystallographic Notes ; by Samuel L_ 

 Penfield. 



1. On Hilbnerite. 



a. From the North Star Mine, Sultan Mountain, Silverton, 

 San Jnan Co., Col. 



The specimens which were used for crystallographic examina- 

 tion were from the private collection of Mr. Geo. L. English, 

 of Xew York. The occurrence of well terminated hiibnerite 

 crystals is not without interest, as our knowledge of the crystal- 

 lization of this species is at present confined to a description, 

 by Professors P. Groth and A. Arzruni,* of artificial crystals. 

 These were not sufficiently developed to admit of an accurate 

 determination of the crystallographic constants, although the 

 authors were able to show a close similarity in form and angles 

 between artificial MnW0 4 and FeW0 4 and the mineral wol- 

 framite (Mn, Fe)W0 4 . 



The ore, in which the hiibnerite occurs, consists mostly of 

 quartz with galena, pyrite and tetrahedrite disseminated through 

 it. Cavities are lined with drusy quartz and contain crystals 

 of hiibnerite, tetrahedrite and occasionally very pretty rhom- 

 bohedrons of rhodochrosite. The hiibnerite usually occurs in 

 groups of radiating and divergent, long-prismatic crystals ; 

 these are often coated with a thin layer of drusy quartz, which 

 sometimes can be removed, by gentle pressure, leaving the 

 prismatic faces smooth and glistening but as the faces at the 

 termination of the crystal are usually rough, the quartz coat- 

 ing adheres there more tenaciously. On one specimen, groups' 

 of these long-prismatic crystals, covered with quartz, were 

 found in one cavity, while in another, less than two inches re- 

 moved, short-prismatic, doubly terminated and isolated crystals 

 were found, which were not coated and which served for ac- 

 curate crystallographic measurement. These crystals, which 

 measure about 4 mm. in the direction of the ortho-axis, have 

 the habit shown in the accompanying figure. The forms 

 which were observed are : 



b, 010, i-l t, 102, -H 



ra, 110, I /, Oil, l-l 



q, 830, £J co, 111, -1 



* Pogg. Ann., cxlix, p. 236, 1813. 



