﻿Vol. 6 1.] MICKOSCOPIC STEtrCTUHE OE SEKPENTINE. 705 



about half of the rock ; the flakes of the mica-like mineral are 

 slightly shorter and stouter than is usual, and its low polarization- 

 tints are of a more ' chalky ' white. Its extinction sometimes 

 appears slightly oblique, which, however, may be due to strain. It 

 can hardly be anything but antigorite, but it occasionally resembles 

 one variety of chlorite. The yellow mineral is perplexing : the 

 granules have no regular outlines, though one or two seem slightly 

 elongated. Their general aspect suggests a rather impure epidote, 

 but they remain dark between crossed nicols. 1 We must be content 

 with suggesting the possibility of perofskite. A. third contains a 

 rather fibrous mineral, associated with the antigorite, which, in 

 polarization-tints, extinction, and general aspect, corresponds best 

 with actinolite. There is also a vein occupied by calcite, probably 

 rather dolomitic. 



A specimen collected from a block in the stream near Mauls, 

 below the Sengesthal, is so very like the first of the three from 

 near the Sterzinger Hiitte, that it is enough to say that the flakes 

 of antigorite are slightly smaller and the folding is not quite so 

 conspicuous. 



IX. The Mateei Seepentine. 



Here, on the northern slope of the Brenner Pass, a much- 

 crushed ophicalcite has been worked in a large quarry, on the steep 

 hillside near the hamlet of Pfons. The specimen examined consists 

 so largely of carbonates — calcite with some dolomite — that we are 

 unable to draw any conclusion from it, the flaky mineral presenting 

 more resemblance to an ordinary mica. The most interesting out- 

 crop of serpentine is at the northern end of Matrei village. Here 

 the river sweeps in a more than semicircular curve round the base 

 of a crag crowned by a castle. On its southern face is serpentine, 

 apparently intrusive in a muddy-looking limestone, the horizontal 

 strata of which are displaced by slight faults. Difficulties of 

 access interfered with close examination, and made it impossible to 

 obtain a junction-specimen, but slices have been examined from the 

 two rocks at the distance of a few yards and from other parts of 

 the crag. Of the former, one is a very fine-grained dolomite, 

 which might either come from the Trias or be a pulverized member of 

 the calc-mica-schist group, to which several other specimens, though 

 modified by pressure, probably belong. Miss Raisin found the 

 serpentine to be blackish or invisible green in colour, with a 

 resinous lustre ; brittle, much jointed, almost crackled ; more 

 compact and smooth-looking on a fresh fracture, and softer than the 

 Sprechenstein rocks ; showing occasional small weathered enstatites, 

 and altogether more like a ' black ' serpentine from the Lizard. 

 A specimen from behind a small shrine proves to be greatly crushed 

 and altered, consisting of a minute fibrous mineral, resembling- 

 talc, but with duller polarization-tints, in which (as in the talc- 



1 Occasionally a small grain seems to produce some effect, but this may be 

 due to the interposition of a flake of the mica-like mineral. 



