126 B. KOTO 



the secondary basaltic hornblende exhibit any signs of a fibrous 

 structure. The diallage-core is traversed by fine lines due to its 

 lamellar structure, and these lines sometimes directly proceed into the 

 hornblende-substance. PI. Ill, fig. 1. is drawn fi:om the polished 

 surface of the rock to half the natural size, and this shows how the 

 marginal black hornblende is related to the diallage. The portion 

 marked (a) between the core and the outer irregular zone is the spot 

 where, when seen under the microscope, the hornblende sends out 

 tongues and shreds of its own substance into the diallage, thus 

 presenting the T^sQwao-eutaxitic structure. The green, compact 

 hornblende of secondary origin is also found in connection with the 

 brown variety, or sometimes developed independently ; and both 

 finally resolve themselves into a fibrous confused mass after passing 

 through an intermediate stage of tremolite. 



Now, the question is at once suggested: — Why should the brown, 

 basaltic hornblende described before have all the appearance of a fresh 

 mineral, while the green, compact variety as well as the diallage-core 

 itself show more or less a fided aspect? The keenest observers have 

 hithei'to passed over this point in silence. First of all, we may ask 

 ourselves whether the fine lamellar structure present in the diallage 

 before as has existed since the formation of the crystals, or whether 

 it is simply a result of pressure, by the action of which the molecules 

 composing the mineral have been enabled to rearrange themselves in a 

 new position for the production of the polysynthetic lamellae. Leopold 

 von Werveke^) thinks it not altogether impossible that these lamellœ 

 could be produced by the influence of mechanical power from outside; 

 but it is not vet decided whether these should be considered as a 

 twinning structure, or only an apparent one. Anyhow, the lamellae 

 may be regarded as having a pathological significance resulting from 

 the action of external force. 



1) Neues Jahrb. f. Mineralogie etc., 1883, II, p. 99. 



