Vol. 54.] 



SCHISTS OF THE ST. GOTHARD PASS. 



365 



the last sometimes so abundant as to give a rather ' dirty ' aspect to 

 the mineral. It shows occasionally a rude cleavage and slight local 

 depolarization, indicating strain. Sometimes idiomorphic crystals 

 occur, but in other cases one part retains the external angles, 

 while the remainder has an irregular outline. A few of the crystals 

 appear to have been more or less broken up, the larger fragments 

 still lying almost in contact. But more usually either the whole 

 grain, or at any rate a part of it, exhibits that peculiar granulated 

 character and partial intermixture with the groundmass which in 

 a garnet prove crushing.^ One or two isolated fragments occur 

 in the slices, but, as a general rule, there are no marked indications 

 of shearing, nor is the mineral distinctly flattened, as sometimes 



Pig. 5. — Biotite including a small jiake of the green variety [oppo- 

 site to a], luith grains of iron oxide and groundmass. {From 

 a small quarry rather higher than that mentioned on p. 358.) 



X60. 



occurs.^ The appearances suggest that the original crystal has 

 been more or less cracked, sometimes a little deformed, while 

 occasionally a portion has been shattered and mixed up with other 

 pulverized minerals in its immediate vicinitj'. 



(3) Staurolite. This mineral seems to occur only where the 

 garnets are abundant, and is never plentiful or large. It is not a 



^ It is well represented in the coloured plate accompanying Mr. Gr. Attwood's 

 paper (Quart. Journ. Geol. Soc. vol. xliv, 1888, p. 636), and described in my 

 note, ihid. p. 651. 



'^ See, for instance, Proc. Eoy. Soc. vol. slii (1887) p. 322, 



