﻿704 PEOE. T. G. BONNEY AND MISS C. RAISIN ON THE [Nov. 1905, 



of crushing, and consists of calcite (the most abundant), a colour- 

 less acicular hornblende (clearly secondary), some residual granules 

 which may be augite, and flakes (not numerous) of the low-tinted 

 serpentine. 



Turning now to the vein already mentioned, we find the matrix 

 to be a dolomitic calcite, and the greyish material embedded in 

 it to be a rather prismatic mineral, resembling an augite, granules 

 of which are apparently enclosed, though these afford only low 

 polarization-tints like the flaky serpentine and extinguish at small 

 angles. 1 This suggests that we have here an altered condition of 

 the latter mineral, but that, owing to the absence of some necessary 

 factor, it has not yet become antigorite. 



VIII. The Sattelspitz District. 



The Sprechenstein outcrop, according to Dr. Hussak, is the 

 westernmost of a zone which extends, with some interruption, from 

 the Sattelspitz, at the head of the Sengesthal. Of this mountain 

 Miss Raisin was not able to make more than a hasty examination, 

 but she observed that the crags of green serpentine cropping out 

 on the slopes of its broad combe exhibited a schistose structure, 

 with a rough east-to-west strike. She collected specimens from the 

 screes and abundant debris below, six of which have been sliced. 

 All show the usual flaky mineral (antigorite) with more or less 

 of the ' thorn- structure,' and occasional streaking along a line of 

 crush. They differ only in the greater or less amount of ' ophitic 

 structure ' and of residual augite. One slice contains this mineral 

 in fair-sized grains of a pale brownish colour, which sometimes 

 exhibit a well-marked diallage-cleavage. The antigorite shows a 

 slight tendency to follow the latter, but none whatever in regard to 

 any prismatic augite-cleavage. 



Beyond the Wilde Kreuzspitze (northward of the Sattelspitz) is 

 the Burgumerthal (a tributary of the Pfitschthal, joining the 

 Eisack just below Sterzing). On the sides of the valley serpentine 

 crops out, apparently intrusive, among gneiss and schist. Speci- 

 mens were collected from the screes below, near the Sterzinger 

 Hiitte, from which three slices have been cut. One consists of 

 some crushed iron-oxide (occasionally showing the ophitic structure) 

 and a little residual augite, but mainly of the clear, colourless, mica- 

 like antigorite, with the usual low polarization-tints, the length of 

 the flakes running up to about "03 inch. Foliation is con- 

 spicuous, with here and there sharply-arched flexures (PI. XLV, 

 fig. 4). Another specimen contains a considerable amount of 

 residual augite, and rather less of a dull-yellow granular mineral. 

 The augite, which looks as if it had been somewhat affected by 

 pressure, is slightly banded, and, where most abundant, forms 



1 This abnormal extinction seems not unfrequent in the residual augite of 

 these Alpine serpentines with antigorite, and is to some extent comparable with 

 the well-known change of the former mineral into uralite. 



