504 Hewett and Shannon — Orientite, a new 



The formula derived from tlie final column of ratios is 

 then : 



4CaO.2Mn2O3.5SiO2.4H2O. 

 This may be expressed as a hydrous orthosilicate thus : 



Ca,Mn,(SiOj5.4H20. 



The water is not given off much below a red heat and in 

 this it behaves like constitutional water and it is perhaps 

 possible to regard it as such. This may be done by 

 making half of the water acid and half basic, the formula 

 then being written : 



H,Ca,(MnOH),(SiOj5. 



The condensed percentages of the average column of ana- 

 lytical figures are compared with the theoretical composi- 

 tion required to satisfy this formula as follows : 







Average 



Theory 







per cent. 



per cent. 



CaO 



.. 22.47) 



23.39 



24.56 



MnO 



92j 







AI2O3 . . . . 



. . 1.081 







Fe.03 . . . . 



.. im\ 



34.91 



34.56 



Mn203.... 



.. 32.27 







SiO., 





32.48 



33.00 



H,0 





7.93 



7.88 



Total . . . 



98.71 



100.00 



The agreement is satisfactorily close, especially when the 

 difficulty of securing pure material is considered. 



Pyrognostics. — The mineral yields neutral water in the 

 closed tube with or without decrepitation. The roasted 

 and dehydrated material is brownish-black in color with 

 a brownish-black streak and is opaque under the micro- 

 scope. In the forceps before the blast the mineral fuses 

 readily with pronounced intumescence to a blebby black 

 glass. It reacts for manganese with the fluxes. 



Relationships. — A search of the literature has revealed 

 no mineral to which orientite is closely related. The only 

 other mineral which contains manganic manganese in 

 similar ratio. is kentrolite which is similar crystallograph- 

 ically and the possibility of including the new mineral 

 in the kentrolite group has been carefully considered. 

 The similarity is shown by the following comparison : 



