126 



PERIDOTITE. 



from this region was found composed of serpentine, witli olivine fragments, and magne- 

 tite. Another serpentine rock contained only serpentine, diallage, and magnetite.* 



Thorsviff, Norway. 



This rock is stated by Mohl to contain 60 per cent of olivine, 30 per cent of enstatite, 

 and 10 per cent of anorthite and magnetite. The olivine and anorthite were in grains, 

 and the enstatite in table-like forms, without crystalline contour.f 



Birkedal, Norway. 



From Birkedal, Korway, according to Mcihl, was obtained a peridotite composed of 

 olivine and enstatite, with some magnetite, chromite, mica, and anorthite — the latter 

 mineral composing about 10 per cent of the rock-mass. J 



Hovden, Horningdal, Norway. 



This peridotite, according to Mohl, is composed of olivine grains and enstatite plates, 

 with magnetite and brown mica. The enstatite is in part of a light yellowish-gray, and 

 in part a very strong nacarat color. It is cut through by parallel fissures, is fibrous, and 

 contains many loose aggregates of brown needles and lamin;v.§ 



Rodfjeld, Norway. 



Ur. H. von Molil described a rock from Eodfjeld, Murusjo, Norway, as made up of 

 olivine grains, enstatite, and a little ledge-formed feldspar. The olivine in places is 

 described as suffering a total change to chrysotile. || 



Andestad See, Aiire, Norivay. 



This stone, according to Mohl, is composed of 75 per cent of olivine in angular grains, 

 20 per cent of enstatite and tabular-formed aggregates, and 5 per cent of chromite in 

 granular aggregations. 



Only a small portion of the olivine remains clear and fresh. Around the contour of 

 the freshest grains wind strings of a dirty greenish-yellow chrysotile. The grains them- 

 selves are sometimes of a dirty grayish-yellow color or cloudy, and show aggregate polar- 

 ization. Here and there a grain is entirely changed to a nearly opaque liver-brown 

 serpentine. 



Tlie enstatite is nearly colorless, beautifully cleaved, and here and there is finely 

 fibrous — tlie fibres being parallel. \ 



In part, this rock is so far changed to serpentine, that only here and there do the 

 olivine grains show any clear central portions remaining. The enstatite remains in part 

 as fresli as in the preceding, except in its cross fractures, which are filled with chrysotile. 

 In part, the enstatite is completely serpentinized, but recognizable on account of its 

 platy pores and its parallel fibrous structure. The chromite remains unchanged. ** 



A section of the Andestad- See peridotite, purchased from Eichard Fuess, of Berlin, 



* Ncues Jahr. Miu., 1879, p. 422. 

 % Nyt Mag., 1877, xxiii. IIG. 

 II Nyt Mag., 1877, xxiii. 113, lU. 

 ** Nyt Mag., 1877, xxiii. 119, 120. 



t Nyt Mag., 1877, xxiii. 115. 

 § Nyt Mag., 1877, xxiii. 116. 

 \ Nyt Mag., 1877, xxiii. 118, 119. 



