124 B. KOTO 



lamellar texture. Seen under the microscope these patches consist, 

 for the greater part, of a long, fl^iky, almost colourless or bluish-green 

 variety of amphibole, a part of which has alretidy chimged intu a light- 

 green, confused mass of serpentine. The above-mentioned amphibole 

 is ? treiiiulitc (c : c = 11°- lo°) of the secondary origin, produced from 

 a diallage-like, greenish -brown pyroxene, the remains of which can 

 frequently l)e met with in the still fresh cores accom])anied with the 

 dark-hrown, hujhhj pleochroic vianjin of the seconikinj, compact, hasaltic 

 Jiontblcnde (c:c — always 1°- 2^ greater than that of the green one). 

 The last variety of am[)hibole is of a very special interes':. 



In petrographical works on gabbros, there has been nuicli dis- 

 cussion aljout the hornblendes which occur in connection with the 

 augite in the gabbro rocks, whether the minerals are of the primary or 

 secondary nature. The hornblendes are principally of 3 kinds Avhich 

 will now l)e considered — (1) the green, fibrous, uralitic ; (2) the compact 

 (jreen; and (o) lastly, the hruicn, compact hornhleiide All writers seem so 

 far in acc(n'd as to the secondary nature ()f the first variety ; but the 

 second and the third have in common the compact texture, dilfering 

 from each other only in colour, thus the appearance of both betrays 

 the original freshness. On this account, J, H. Kloos^^ was led to say 

 that, of tlie hornblende which encircle the core of the intact diallage, 

 " die Annahme einer Umwandlung des Diallags in die compacte 



Hornblende scheint mir von vornherein ausgeschlossen zu sein 



Die randliche \^erwachsung von Diallag und Hornblende würde als 

 einfache Perimorphose zu deuten sein." 



Lately, this question became one of paramount importance in 

 petrography, especially in explaining the genesis of amphibole-schists 

 and the " tlasergabbros," and has already received much attention 



1) Neues Jahrb. f. Miueralogie etc., Ill Beilage-Baud, p. ä2. 



