113 



green and blue schistose serpentines at Sprechenstein, near Sterzing. Both 

 the massive and schistose varieties from the last mentioned locality have been 

 carefully investigated by HUSSAK. 



The green schistose serpentine from Sprechenstein is principally 

 composed of scales of a light green mineral with a perfect cleavage of the 

 mica type. Sections at right angles to this perfect cleavage are lath-shaped. 

 They give straight extinction and are distinctly pleochroic ; leek-green when 

 the short axis of the nicol is parallel to the cleavage cracks, colourless when 

 the short axis is at right angles to these cracks. The double-refraction of 

 this mineral is slight. Cleavage flakes show in convergent light the optic 

 picture of a biaxial crystal with small axial angle. The double refraction is 

 negative, and the negative bisectrix agrees with the vertical axis. The 

 dispersion is well marked, /> > v. 



The mineral was isolated by means of the solution of bi-iodide of mercury 

 and potassium, and gave the following analysis : 



i. n. 



Si0 2 ... ... 41-14 ... ... 41-58 



Fe,0, ... ... 3-01 ... ... 7-22 



A1 2 3 ... ... :!.*2 ... ... 2-60 



CaO ... ... 0-40 



MgO ... ... 39-10 ... ... 3G-.Su 



H.O ll.s;. 12-67 



<)!):} 100-S 



I. Antigorite from serpentine of 



IT. Do. from Antigora, Piedmont. 



It thus appears that this mineral agrees in chemical and optical characters 

 with the antio-orite described by DES CLOISEAUX. The difference in the 



O * 



amount of iron may be explained by the fact that the mineral from 

 Sprechenstein was entirely free from magnetite. 



Lying between the antigorite scales were grains of magnetite and 

 colourless granules of a mineral which gave strong refraction and double- 

 refraction. The larger of these colourless granules showed sometimes two 

 parallel sets of cleavage cracks meeting at 90, and sometimes only one set of 

 parallel cracks. In the latter case the maximum extinction, referred to the 

 cleavage cracks, was 42. Sections with one set of parallel cleavage cracks 

 and straight extinction (sections parallel to the ortho-pinacoid (100) of an 

 augite-prism) showed an optic axis in convergent light. These characters 

 show that the mineral in question is an augite, poor in iron (Salite). 



A brown augite with a perfect cleavage parallel to (100) also occurs 

 sparingly in the rock. This is referred to diallage by the author. Vividly 

 polarising grains of talc are often associated with this diallage. The other 

 minerals of the rock are a green chlorite and staurolite. The latter mineral 

 occurs as small round grains and, more rarely, as columnar crystals. It is 

 yellow in colour and shows a marked pleochroism ; 7, dark honey yellow ; 

 ft and n, pale yellow. 



