Larsen and Steiger — Sulphatic Cancrinite. 



333 



Physical properties. — The sulphatic cancrinite is nearly 

 colorless ; has a hardness of about 5 ; and fuses readily with 

 intumescence. It is readily soluble in acid with effervescence 

 and yields gelatinous silica on heating. The specific gravity 

 is 2-443. 



Optically it differs considerably from cancrinite ; both 

 minerals are uniaxial negative, but the mean index of refrac- 

 tion of sulphatic cancrinite is considerably lower than that of 

 cancrinite, and the birefringence is much lower. The follow- 

 ing data for sulphatic cancrinite are from the analyzed 

 material. The different grains differ slightly — perhaps ±-002 

 — in index of refraction. The optical properties of cancrinite 

 and natrodavyne are given for comparison. 



Sulphatic cancrinite 

 Colorado 



Cancrinite 



Natrodavyne 



to = 1-509 



1-524 



1-522 



e = 1-500 



1-495 



1-527 



to — £ = -009 



•029 



•00Y 



Optical character + 



+ 



— 



Sulphatic cancrinite shows a poorly developed cleavage 

 parallel to the prism faces ; rod-like inclusions and negative 

 crystals are commonly arranged parallel to the prismatic axis. 



Chemical Properties. — The results of a chemical analysis 

 made by George Steiger on carefully selected material which 

 contained very little impurities are given in column 1 of the 

 following table. Column 2 gives the combining ratios corre- 



Analyses and ratios of sulphatic cancrinite and of cancrinite. 





Sulphatic 



Average 



of three 



Cancrinite 





cancrinite 



cancrinites* 



Litchfield, Maine f 







Combin- 





Combin- 





Combin- 





Analysis 



ing 

 ratios 



Analysis 



ing 

 ratios 



Analysis 



ing 

 ratios 



SiO, 



33-70 



34-9 



37-31 



37-3 



36-19 



36-3 



ai 2 o 3 



29-40 



18-0 



28-22 



16-6 



29-24 



17-4 



CaO 



4-18 



4'6 



5-18 ) 



230 



4-72 



5-1 



Na,0 



18-52 



18-7 



16-88 V 





19-20 



18-7 



K a O 



1-45 



1-0 



1-74 ) 





•14 



•1 



H a O- 



•72 



-.. 











H,0 



4-24 



14-7 



4-53 



15-1 



4-15 



14-0 



TiO, 



•07 







... 



... 







co, 



3-18 



4-5 



5-89 



8-0 



6-11 



8-4 



so 3 



4-65 



3-6 











SrO 



•08 



--- 



... 



... 



... 



— 





100-19 



100-0 



99-75 



100-0 



99-75 



100-0 



* One from Ditro, two from Brevik. f Steiger, analyst. 



Am. Jour. Scr.— Fourth Series, Vol. XLII, No. 250.— October, 1916. 

 23 



