ad on seem to show that the diopsides among the pyro 
tion 
crystals have heretofore been described. In the 
662 General Notes. 
Mineralogical News.—In 1871, Tschermak discovered that 
optical characteristics of the various pyroxenes depended in great 
measure upon the proportion of their iron constituent. He found 
that with increase-of iron there was a corresponding increase in i 
the size of the optical angle, and also in the inclination of the © 
acute bisectrix to the vertical axis of the monoclinic varietit 
In later years Wiik, Herwig, and Doelter examined monoclinic | 
pyroxenes with the view of deciding as to whether Tschermak’s” 
observations would be found to apply generally. Their results, 
however, were not conclusive. Very recently G. Flink* of Stock- 
holm, declares, as the result of investigations made on diopsidi, 
schefferite, and rhodonite, that the crystallographic angle varies 
with variation in the percentage of iron, increasing with the in- 
crease of this constituent and decreasing with its decrease, but 
within very small limits (22’). The morphotropic action of man- f 
ganese is to diminish the size of the angle and to carry the erys- 1 
tallization of the pyroxene over to the triclinic system. „E 
value of this angle for different proportions of manganese is given 
as follows: if 
Diopside (Mn = free). Schefferite (MnO = 8.32 %). Rhodonite (MnO = 41.88 fi 
74° 11/ 73° 53’ 71° 15%” 
A 
B ‘ 
E 
Z 
The optical angle and the angle of extinction in the plane of 
symmetry both increase with the rise in the percentage either of 
iron or manganese. The geometrical, optical, and chemič 
orm a continuous series analagous to the plagioclase series am 
the feldspars——In the course of the above investigation Fli 
i following new forms: P3, P7, P=, —2Pa, — $P and 
_ Schefferite is the name given by Mikaelson to a ma 
rich diopside from Långban. According to Flink its co 
is: 
SiO, CaO MgO MnO 
52.28 19.62 15.17 8.32 
_ of the pyroxenes. The axial ratio is: a:b : c = 1.1006: 1:0. 
Zeitschrift f. Kryst., xi. p. 449. 
