I92I. No. 8. ox THE ECLOGITES OF NORWAY. 37 



without feldspar, as a hornblende-peridotite. Of both kinds of rocks there 

 are actual examples with sufficient approximation of the composition to the 

 above figures. 



Our eclogite is actually composed of garnet, clinop yroxene, pale 

 green hornblende, olivine, black iron ore, rutile and a little apatite. 



The garnet has 



"d= I-7585- 



As the rock-analysis indicates that this garnet, like all the eclogite 

 garnets from Sondmore analyzed, must be low in lime, we ma}' safely 

 assume its composition to be between those of the garnet from Almklov- 

 dalen (n = 1.7498I and from Silden in Selje In = 1.7660I, and calculate it 

 graphically from their refractive indices. We obtain the following percentage 

 figures: 41. i SiO.,, 22.4 ALtO^, 1.7 Fe.,03, 16. i FeO, 0.4 MnO, 14.1 MgO 

 and 4.9 CaO, conforming to the atomic formula (Fcg^Mg^^Ca^gl. From our 

 diagram (fig. i, p. 9 1 would result iFe^^Mg^^Ca^^,). 



The amount of garnet may be estimated at 55 per cent. The compounds 

 entering into it having been subtracted from the bulk analysis, the rest 

 shows (Mg,FelO in large excess over the lime in the diopside ratio, and 

 little alumina. The largest part of the remainder consists of cl i no- 

 pyroxene in long prismatic anhedral crystals. This pyroxene probably 

 contains greater part of the alkalies in the rock, but it is not so rich in 

 alkali as the pyroxene in the eclogite of the Duen type. The pale green 

 hornblende occurs much in the same manner as the p3Toxene, in the 

 form of long prisms. 



The olivine occurs as more rounded individuals which are always 

 intergrown with black iron ore. The intergrowth has some resemblance 

 to myrmekite, but it is present in almost all the olivine. The axial angle in the 

 latter is almost 90 ' indicating a mixture with about 10 per cent fayalite. 

 The olivine is always accompanied by a bright brown iddingsite-like mineral. 



Iron ore, probably ilmenite, also occurs as larger anhedral crystals. 



The foliated structure of this eclogite is due to a parallel arrangement 

 of the pyroxene and hornblende prisms and the elongated groups of garnet 

 crystals (fig. 3 pi. I). 



The eclogite in Lyngenes, though occurring in gneiss, shows more 

 resemblance to the eclogite in Almklovdalen which is in olivine-rock than 

 to any of the other occurrences in gneiss investigated. Chromic oxide, 

 however, is only present in traces, and the alkalies are somewhat more 

 abundant. 



The Eclogite from Sildcii, Xoriifjord. 



A specimen of eclogite from a lens in gneiss, i m long, occurring on 

 the island Silden in Selje and collected by H. Reusch, was subjected to a 

 quantitative investigation. 



