OCCURRENCE OF ISOLATED AUGITE CRYSTALS, ETC. 



well as two gnomonic projections showing the forms present 

 on the crystals. 



Out of about fifty specimens 

 collected only two gave satis- 

 factory results on being measured 

 with the goniometer. The general 

 habit of these crystals is shown 

 in the accompanying figure. The 

 forms developed in the prism zone 

 are the pinacoids [100] and [010] 

 and the prism [110]. The other 

 forms appear to be in one case 

 the dome [011] and in the other 

 case the pyramid [111 J. On the 

 other crystals the faces other 

 than those on the prism zone 



were dull, apparently by reason of being corroded by the 



sea-water. 



The measurements were made on a Goldschmidt two-circle 

 goniometer and the results have been tabulated, together 

 with the angles given by Goldschmidt for diopside in his 

 " Orystallographische Winkeltabellen." In addition to the 

 forms recorded, several very small and duli faces are 

 present on some of the crystals which could not be measured 

 accurately, but which seem to belong to the forms [021] 

 and [121] or [1.21] and [221] according as the larger faces 

 are [011] or [111]. The differences between the theoretical 

 angles for these forms are so small, however, that it is 

 impossible to distinguish between them when the faces are 

 so dull as in the present case. If the correct orientation 

 of the crystal were known this ambiguity would of course 

 disappear, since it would be evident whether the faces were 

 on the back or the front of the crystal. It is impossible, 

 however, to determine this orientation excepting in the 



