Review of Recent Geological Literature. 421 
Tin- bell of itabirite in Ranen lias a length of from twentj to twenty- 
five miles. In Dunderlandsthal we nleel two immensely thick limestone 
strata, corresponding to each other in every respect, each of which is a 
limb of an anticlinal told and has below it the bed of itabirite. The 
thickness of the latter is here aboul sixty to seventy-five feel on the av- 
erage; but at Kvitinge, where in other respects the stratum is lean, it is 
no less than 290 to 330 Feet in thickness. 
There is also almost complete correspondence between the two iron 
ore strata at Naeverhaugen and those at Kanen. In both regions we find 
principally hematite (Fe 2 Og). In Dunderlandsthal it is developed as 
the specular or micaceous variety, and there is but little magnetite; 
then quartz, with some hornblende, biotite, garnet, epidote, feldspar, 
very little calcite. titanite. etc.: added to all of which is a mingling of 
apatite, amounting to aboul 1 percent, on the average; very little sul- 
phur and titanium: less than 1 per cent, of manganese; even the slag- 
forming elements (Si0 2 , A1 2 C>3, ( ';' () . MgO, etc.) agree almost per- 
fectly in thin sect ion. 
The ore-bearing stratum consists of a series of layers varying widely 
in iron content. — from about 10 or 20 to 00 or 65 per cent . Single layers 
are occasionally so rich as to be exploited, but as a whole the stratum 
must be considered, in most localities, rather poor in iron. Nevertheless 
the total content of iron (especially in Dunderlandsthal. where the itab- 
irite has a greater development than at any other locality known in 
Europe) is of ureal importance and can only be compared with the iron 
mountains of northern Sweden. Gellivara, Kirunavara, etc. 
The Cambrian (".') iron ores of Nordtand find their closest analogy in 
Sweden with the so-called "Torrsten" ores ("Trockenerz," /.'..ore 
which gives a dry or siliceous slag on being smelted). Both these ores 
are accompanied by a superabundance of quartz and acid silicates: but 
by very small amounts of carbonates and basic silicates. In both cases 
there is usualh considerable apatite, very little sulphur, comparatively 
little manganese, and verj much hematite in proportion to the magne- 
tite. In line, the ••Torrsten" ores are distinguished from the other Ar- 
chean iron ores h\ appearing more like normal strata and less like short 
lens-shaped masses. 
The ••Torrsten" ores are also related to the other iron ores in central 
Sweden belonging to the same general division. We thus arrive at the 
conclusion that the Swedish iron ores of the Dannemora Persberg 
Norberg Grangesberg type, belonging to the Archean formation, as well 
as the Norwegian ores of the Arendal-Krageroe type, were formed in 
the same manner as 'the apparently Cambrian ores of the Naeverhaugen- 
Dunderlandsthal type.* 
*Besides this class of iron ores, the following .ire represented in Scandinavia: 1. 
Iron ores formed by pnounvitolytic processes; '_. BBgregationa in basic eruntive rooks; 
also, the ore deposits of the Gellivara Kirunavara type, winch are not associated 
with limestone and do not correspond with the Dannemora Persberg Arendal- 
Naeverhaagen type in that respect. For this reason no attention is paid here to the 
iron ores of northern Sweden, nor to the ores occurring in the "tiefen Urgneiss" of 
Norway. 
