SCHEERER LIMESTONE IN CRYSTALLINE SCHISTS. 1 1 



also (which at a locality near the Gill-Vand occur more than 2 inches 

 in length) are isolated, and limited to the garnet and vesuvian zone. 

 Augite (the so-called Funkite) occurs as a widely distributed ingre- 

 dient in some of the calcareous beds. Crystals, of the size of a mus- 

 tard-seed up to the length of some lines, are scattered through the 

 whole of the calcareous mass and give it a peculiar pmictated appear- 

 ance. Where the usual coating on the limestone is wanting, we meet 

 with it on the gneiss and often to a somewhat greater extent. We 

 can also here recognize that the hornblende, which is present as a 

 more or less predominating ingredient of the gneiss, is converted into 

 augite by the contact with the limestone. This is visible in a band 

 at places scarcely more than 1^ to 1 inch broad ; sometimes, however, 

 it penetrates deeper in the gneiss, the structure of which is otherwise 

 unchanged. As regards the rest of the minerals above-mentioned, 

 their occurrence is quite sporadic. The chondrodite is interspersed 

 here and there ; and sometimes its imperfectly formed roundish 

 crystals are gathered into nests and small groups ; as is also the case 

 with the spinel-ruby, mica, and magnetic pyrites, which we find also 

 in small parcels at other places in the limestone. 



Crystalline Limestone of the Bistrict of Arendal. — Arendal lies 

 about 8 miles to the north-east of Christiansand, and within the same 

 great gneiss district of South Norway. In the limestone of Christian- 

 sand we found evidence enough to lead us to theorize on the origm 

 of the rocks and the formation of their mineral contents ; but the 

 phenomena of the Arendal limestone are ambiguous enough. The 

 numerous scattered nodules, veins, and patches of crystalline lime- 

 stone, or rather of extremely coarse-grained compact calc-spar, occur 

 indeed partly in indistinctly, and sometimes horizontally, bedded 

 gneiss, yet they are met with also in connection with the great layers 

 of magnetic iron of this district in steep and vertically bedded gneiss. 

 The general and great mineral richness to which Arendal owes its 

 fame in the mineralogical world is due in no small degree to the oc- 

 currence of the crystalline limestone. This rock contains. Garnet 

 (with Colophonite), Augite (with Coccolite), Epidote, Hornblende, 

 Oligoclase, Orthoclase, Quartz, Scapolite, Sphene, Apatite, Zircon, 

 Spinel-ruby (very rare), Chondrodite ?, &c. The total absence of 

 vesuvian is conspicuous in comparing these -with the Christiansand 

 group of minerals. Epidote, which does not occur at Christiansand, 

 is here one of the abundant minerals. Its crystals, as far as 

 my experience goes, are always set upon the gneiss ; and in some 

 measure they represent the vesuvian. The garnet crystals occur in 

 like manner, still they are found (especially the colophonite) imbed- 

 ded in the limestone mass. The same holds good with the augite ; 

 its fixed isolated crystals appear mostly as coccolite, and re})rcsent 

 the augite (funkite) of the Christiansand district. At a few places, 

 as, for example, near the Barbo mine, we see garnet and epidote 

 fpistazite), like layers alternating one with another, and so in some 

 measure representing the gneiss, which here exhil)its the same stratifi- 

 cation as tiie former. At Arendal I have examples of the coating of 

 the limestone quite corresponding tn that al the last- described 



