138 On the Chemical Composition of Wernerite, 
moved, for the percentage is lower than any of the other 
minerals, the oxygen ratio of SiO, : R, O, being 4 : 1:73; 
but it is difficult to perceive in what manner this has taken 
place. There is likewise a remarkable deficiency of peroxide 
of iron, compared with other altered scapolites. 
The fact that this mineral has so closely the composition 
of mica, and yet is not, like the last mentioned, converted into 
it, 18 very curious. 
3. Red Scapolite from Arendal. 
Density 2°852. Evidently much altered. Occurs together 
with black hornblende in the magnetite beds of Arendal. 
Analysis gave :-— 
I. Il. 1g eo 
Silica, ; ; 59-74 We 59°74 
Alumina, . , 23°86 16°44 16°20 
Peroxide of iron, . Aé 7°90 7°90 
Lime, ‘ i 2°24 2:05 2°15 
Magnesia, . : 3°90 4:15 4:02 
Potash, : ; — 4°42 4°42 
Soda, ' — 4°31 4°31 
Water, ; : 1:83 1:83 1°83 
100°57 
The quantities of oxygen being— 
Silica, : : 31-00 4 
Alumina, . . 757 : ; 
Peroxide of iron, . Oo | } sili a 
Lime, ; : 0°61 
Magnesia, . : 1:66 ; : 
Potash: . 0°75 Sag oe 
Soda, 4 : £10 
This mineral is distinguished by a maximum of silica and 
a percentage of lime less even than in mica. It is remark- 
able that magnesia, potash, and soda, are present in the same 
proportion. The smaller proportion of bases R, O,, and the 
preponderance of potash over soda, is likewise evident. 
The substitution of potash for soda appears, therefore, as 
the characteristic feature of this transmutation. Out of forty 
specimens of Wernerite, to all appearance unaltered, analysis 
shewed that in thirty-eight the quantity of potash was very 
small in proportion to the soda, while in five out of seven 
. 
a ee a ae — ss 
