S. L. Penfield — Crystallization of Willemite. 307 



Willemite from the Sedalia Mine, Salida, Colorado. 



At this locality it was observed in transparent, colorless crys- 

 tals up to 3 mm in diameter, having the habit shown in fig. 4. 

 The mineral was identified by its blowpipe reactions and the 

 following measurements : 



Measured. Calculated. 



e^e, 1102^0112 = 35° 35' 36° 23' 



« A «, 1210^0112 = 71 42 71 4S 



The crystal faces are warped and striated and on some of 

 them low, vicinal prominences are developed, which are un- 

 symmetrical with reference to the 

 rhombohedron e and indicate clearly 

 that the crystals are tetartohedral. 

 When mounted in Canada balsam 

 these rather flat crystals show with 

 convergent polarized light a normal 

 uniaxial interference figure, and a 

 strong positive doable refraction. 



Willemite or Troostite from Franklin, JV. J. 



The crvstals from this locality, which are commonly found 

 imbedded in calcite, are usually rather coarse and show simple 

 combinations of a, 1120 ; r, 1011; e, 0112 and a, 0001. In 

 the private collection of Mr. Frederick A. Canfield of Dover, 

 ~N. J., there are, however, two specimens which are worthy of 

 special description, as the crystals exhibit combinations which 

 are very unusual for the Franklin mines and are also beautiful 

 illustrations of rhomboheclral-tetartohedrism. These speci- 

 mens were kindly loaned to the writer, who takes this oppor- 

 tunity of expressing his thanks to Mr. Canfield. 



r u J&sU 



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- 



On one specimen there were several nearly transparent, 

 green prisms, attached to a gangue of massive willemite and 

 f ran klinite. One of these, about 30 mm long by 20 mm in diam- 



