ON A NEW VARIETY OF HORNBLENDE. 

 By R. a. Daly. 



Presented by J. E. Wolff, February 8, 1899. Received February 11, 1899. 



The abnormal etching characters of the Philipstad hornblende referred 

 to in the foregoing paper have suggested further study of the mineral ; 

 the description of its otlier properties shows that it should be regarded as 

 an independent member of the amphibole group. 



It is a variety given me for study by Professor Berwerth of the Royal 

 Museum in Vienna. It is catalogued in that collection as " A. o. 458, 

 Philipstad, Sweden." In addition to the original cleavage pieces for 

 etching purposes, Professor Berwerth has been kind enough to turn over 

 to me several fine crystals from the parent druse and enough extra 

 material to permit of chemical analysis. To him, in thus abundantly 

 supplying me with the mineral, my best thanks are due. 



The crystals stand upon a compact mass of the same hornblende. 

 The usual planes (110), (010), (100), (130), (Oil), (Tschermak's orien- 

 tation), with normal interfacial angles, are well developed. The adjoin- 

 ing table shows the close correspondence of the observed angles with the 

 calculated angles (cf. Lacroix, Mineralogie de la France) : — 



Observed. Calculated. 



110:130 150° 9" 150° 6' 



010 : 130 147° 23' 147° 29' 



110:110 (faces) 124° 11 '-124° 17' 124° 11 



" " (cleavages) 124° 27' 



110:010 117° 50' 117° 54' 



110:011 68° 33' 68° 46' 



011:011 149° 12' 149° 11' 



The unit prism is usually striated, owing to the presence of vicinal 

 planes. 



The reflexes in the goniometer from the planes of the vertical zone 

 were often considerably displaced. This is probably due to the warping 

 of the crystals. In several of the latter, it is possible to see with the 

 VOL. XXXIV. — 28 



