76 Sterrett — New Type of Calcitefrom Jqplin, Mo. 



plane. The occurrence of G on only one individual of a twin 

 was observed on four specimens, while on the large crystal 

 described above, G occurred on both. 



The crystals show a tendency toward a prismatic develop- 

 ment parallel to the e faces. This was further marked by pits 

 or negative crystals of prismatic form observed on the e faces 

 of one crystal. The faces of the negative crystal were paral- 

 lel to the unit rhombohedrons, and therefore rhombohedral 

 themselves. One crystal, probably from another opening in 

 the same mine, showed the same method of twinning, though 

 this fact was nearly concealed by the development of very 

 large v faces nearly covering the reentrant angle of the twins. 



The development of a twin crystal similar to those described 

 above was observed on a single specimen of golden calcite 

 from the Joplin region about two years ago by Mr. English. 



At his request, a drawing of it was prepared by Mr. H. P. 

 Whitlock ; Mr. English has kindly allowed a copy of the 

 figure to be inserted here for comparison. The letters repre- 

 sent forms found in Dana's System of Mineralogy. Whether 

 other crystals were found and what was the exact locality for 

 this could not be learned. 



In conclusion, acknowledgment is made to Mr. English for 

 generously supplying material for examination, and to Prof. 

 E. S. Dana and Dr. W. E. Eord for assistance in the prepara- 

 tion of this paper. 



Sheffield Laboratory of Mineralogy, 



Yale University, New Haven. 



