88 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.51. 



The ratios of column 4 are as near a definite ratio (1:1:1) as could 

 be expected considering the small amount of material used for analy- 

 sis; and they indicate that in this occurrence, at least, the iron 

 present in titanite is in the form Ca"(Fe'"0)'2(SiOJ'"', or 

 CaFcoSiOc, a compound presumably isomorphous with Ca (TiO) Si04, 

 as yet unknown in the pure state. 



The mineral thus agrees in every essential respect with titanite, 

 being unusual in containing a rather large percentage of ferric oxide, 

 and in possessing an acicular form. 



