﻿Vol. 6 1.] MICROSCOPIC STRUCTURE OF SERPENTINE. 701 



Quite recently two closely-allied minerals — pseudo-regular anti- 

 gorites, to use his phrase — have been described by Axel Hamberg. 1 

 One, from Persberg in Wermland, occurs with magnetite, chlorite, 

 and calcite, in cubic form, measuring from 2 to 5 millimetres along 

 the edge, with cleavage in three directions, one strong ; greenish- 

 white in colour, and pearly in lustre; not harder than gypsum. 

 The other from Kograbe, Nordmark, is a hexagonal, easily-cleaving 

 mineral, yellow-brown in colour, only slightly pearly, with a larger 

 axial angle and more transparent than the other. 

 Analyses are given as follows : — 



Si0 2 43-68 42-90 



A1 Q 3 0-34 0-51 



MgO 3894 39-19 



FeO 4-18 3-90 



MnO trace trace 



H 1203 12-30 



Fl" 2 0-97 



99-17 99-77 



He remarks that these are practically analyses of an ordinary 

 serpentine (H 4 Mg 3 Si 2 9 ) with some replacement of MgO by FeO, 

 and that this mineral seems to fall into two groups — one fibrous, 

 typified by chrysotile; the other leafy, by antigorite. That, as 

 will be seen, quite accords with our own conclusions, but we doubt 

 whether a hard-and-fast line can be drawn between them. 



VII. The Sprechenstein Serpentines. 



Sprechenstein is near the town of Sterzing, on the Brenner 

 road. The serpentine can be traced obliquely up the steep wooded 

 slopes east of the Eisack Valley, the largest mass exposed being 

 in a crag which forms a slightly-convex projection at the foot of 

 the hill, while smaller outcrops are visible higher up. This crag is 

 largely composed of a hard, rather tough, harsh-feeling serpentine, 

 pale green on fresh fractures, weathering to a dark green, some- 

 times purplish on smooth surfaces. The rock is compact, often 

 rather regularly jointed, so as to form big rectangular blocks. 

 Not a little, however, especially at the northern part, is con- 

 spicuously schistose, and the imperfect wavy cleavage-planes often 

 enclose lenticles of the more compact serpentine. The schistose 

 parts are generally not quite so hard or rough to the touch as the 

 compact, are less granular-looking, and a little more mottled with 

 lighter-coloured spots. They are frequently patched or veined with 

 a whitish mineral. A much-crushed gneiss crops out to the north, 

 separated from the serpentine-crag by an interval of the wooded 

 slope. A mass of vein-stuff about 4 feet thick, a description of 

 which is reserved for the present, borders the serpentine, which for 

 the first 20 feet is conspicuously schistose. It then becomes a 



1 Geol. Foren. Stockholm Forh. vol. xxvi (1904) pp. 07-83, 



3d 2 



