Vol. 4] Murgoci. — Classification of the Amphiboles. 



385 



except for the position of the axial plane, they are similar to the 

 hornblende of Wright* found at Beverley. 



In the course of an investigation of riebeckite rocks and their 

 inclusions (from Quincy, Massachusetts, Jacobdeal, Dabrogea, 

 etc.) I was fortunate enough to find this kind of amphibole, 

 which in my notes I have called Lane's amphibole. It is a dark 

 colored amphibole (like barkevikite) , with a very strong pleo- 

 chroism: a = brownish yellow, fa = green or brownish green, C 

 = bluish green or greenish blue; C fa>9. Angle of extinc- 

 tion C:c — 13° in the darker colored, up to. 20° and even 26° 

 (in this case fa : c) . The birefringence y — " is large enough to 

 be noticed, but y — /? is very small, almost zero. 2 V of course 

 very small or zero; very strong dispersion; p < u; optic character 

 negative. In the darker colored lamellae with an excessive dis- 

 persion (fa/3:c<fa v :r), we meet with a transverse axial plane, 2 V 

 very small around the same negative bisectrix. 



Besides the inclusions of riebeckite granite, I have observed 

 this mineral in a section (No. 304, the property of Dr. C. Pa- 

 lache) of glaucophane schist from Riff el Alp (Zermatt). In this 

 section we have in some lamellae the blue-green amphibole with 

 the axial plane parallel to (010) : in others it is transverse to the 

 plane of symmetry; angle of extinction C (or fa) : c = 18°-20°; 

 optic character negative.! All these amphiboles are optically 

 similar; there is also another which differs only in the angle of 

 extinction. 



In Rosenbusch's new manual we find a communication by W. 

 Freudenberg about an amphibole from the shonkinite of Katzen- 

 buckel : black (transparent brown or greenish), "very rich in 

 iron." Pleochroism: 3 = straw color, fa (or C)=deep red- 

 brown, C (or b) = green to yellow-green. Angle of extinction: 

 C (or b) : c variable up to 65° (?); b>:C<& v :C; 2 V very small 

 around a negative bisectrix. Axial plane in the central lamellae 

 parallel to (010), in the periphal zones perpendicular to (010). 



These observations all show that crossite-like amphiboles oe- 



* F. E. Wright, Alkali syenit von Beverley, Tseherm. Mittheil, XX p. 

 310. See Table II. No. X." 



f This amphibole must occur very frequently; for example, I believe that 

 I recognized it in a slide of riebeckite granite from Socotra, although I 

 studied the slide, the property of Professor A. Pelikan, No. 41, for a few 

 minutes only. 



