S. L. Penfield — Crystallization of Willemite. 305 



Art. XXX. — Contributions to the Crystallization of Wille- 

 mite ; by S. L. Penfield. 



As far as known willemite is a mineral of rare occurrence. 

 The manganese variety, troostite, is found at Franklin, Sussex 

 Co., New Jersey, in sufficient quantity to make it a valuable 

 ore of zinc. It also occurs sparingly at the Merritt mine, 

 Socorro Co., New Mexico, an analysis and description of it 

 having been given by Prof. F. A. Genth * In the summer of 

 1891, while collecting for the IT. S. Geological Survey, the 

 writer found a well crystallized specimen on the dump of the 

 Sedalia Copper Mine, near Salida, Chaffee Co., Colorado and, 

 as far as known, thes" three are the only localities for the min- 

 eral in the United States. 



Our knowledge of the crystallization of willemite is limited 

 to a description by A. Levyf of the simple crystals from 

 Moresnet near Altenberg and to measurements with the con- 

 tact goniometer of the large troostite crystals from New 

 Jersey by E. S. Dana:}; and Des Cloizeaux.§ From the simi- 

 larity of the rhombohedral angles of willemite, Zn 2 Si0 4 and 

 phenacite Be„Si0 4 it has been assumed by Grothf that wille- 

 mite probably crystallizes like the latter in the rhombohedral- 

 tetartohedral division of the hexagonal system, but no crystals 

 have ever been described which were sufficiently modified to 

 show the tetartohedrism. 



Willemite from the Merritt Mine, New Mexico. 



Through the kindness of Mr. Geo. W. Fiss of Philadelphia, 

 Pa., the author has been supplied with a suite of specimens 

 containing crystals suitable for measurement on the reflecting 

 goniometer. The crystals are colorless, transparent and meas- 

 ure on the average about 0*5 mm in greatest diameter. Some 

 exhibit a dark center with transparent exterior, or with simply 

 the extremities of the prism clear. The crystals occur as 

 aggregations or as druses lining cavities in the rock. The 

 forms which have been identified are : 



c, 0001, 



O 



e, 0112, 



_i 



2 







a, 1120, 



i-2 



it, 2113, 



f-2J 



or 



|P2 I 

 4 r 



r, 1011, 



1 



v, 1325, 



_ Vr 



or 



3P3 ,. 



4 / 



z, 0111, 



-1 











*Proc. Am. Phil. Soc, xxiv, p. 43, 1887. f Ann Mines/iv, p. 513, 1843. 



% System of Mm., Sixth Edition, p. 460. 



£ Manuel de Mineralogie 1862, p. 43. 



I Tahellarische Uebersieht der Mineralien, 1889, p. 111.. 



