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ECONOMIC GEOLOGY 
[cNEOUS ORES—TITANIFEROUS MAGNETITES 
Veins of hematite, either amorphous or in brilliant crystals 
of specular iron, are formed around volcanic vents where 
iron chloride vapour is decomposed in contact with steam. 
Igneous ore on a larger scale may be illustrated by the hill of 
Taberg in Sweden, which consists of a boss of basic and 
ultrabasic rock. The outer zone consists of olivine-hyperite 
{composed of olivine, the basic felspar anorthite, and rhombic 
pyroxene) rich in titaniferous magnetite. The hyperite 
passes into the rock which Wadsworth (1882) named Cum- 
berlandite: it contains 31 per cent. of iron and is composed 
of olivine and titaniferous magnetite, which are intergrown 
as in ordinary igneous rocks. 
The iron mass at Taberg was formed as a segregation of 
iron oxides in basic igneous rock. It was worked, until 
1870, as iron ore, and a picture of it was published in 1755 
by the Royal Society (Phil. Trans., xlix, p. 34, pl. ii) as a 
mountain of iron. Though this mass, estimated at 100 
million tons, stands beside a railway 8 miles S. of Take 
Wetter, it is no longer worked. as it contains too much 
titanium. 
Enormous masses of gabbro with bands of titaniferous 
magnetite mixed with spinel exist in Northern Sweden and 
Lapland, as at Routivaara. These bands have been repre- 
sented as formed by direct segregation as at Taberg; but 
according to Peterson they include angular fragments of 
gabbro, and there is no transition between ore and rock. 
The bands were formed after the gabbro and not as the first 
stage in its consolidation; they contain 68 per cent. of iron 
oxide, but are valueless at present owing to their 14} per 
~ent. of titanium oxide. 
ConTacT ORES 
Ironstones formed at igneous contacts are well developed 
in the Pacific coastlands of America from Alaska to Chile. 
They usually consist of masses of magnetite at the contact 
of limestone with rocks identified as diorite. The ores are 
actually replacements; they often contain from 45 to 65 
per cent. of iron and are low in phosphorus, but may contain 
so much sulphur as to require roasting. The ore may in-