
A 2 

& 

236 STRUCTURAL AND FIELD GEOLOGY 
the phosphoric acid would be obtained from apatite (common as a 
constituent of igneous rocks) and the manganese from many different 
rock-forming minerals. We may suppose that regional metamorphism 
would bring about marked changes in the original chemical and 
mechanical sediments. What were at first carbonates and hydrates of 
iron would, under the influence of heat in the presence of moisture, 
eventually be transformed into specular iron and magnetite, while the 
clays associated with them would be changed into mica-schist. 
Beds of magnetite and specular iron are associated with 
schistose rocks in many other countries, as in S. Russia, in 
the Riesengebirge, in Spain, in the United States (New 
York, New Jersey, Carolina, Michigan), and elsewhere. 
Carbonate of iron (siderite) is another ore met with amongst 
schistose rocks. At Hiittenberg, in Carinthia, it occurs in 
crystalline limestones which are interstratified with gneiss 
and mica-schist (see Fig. 85). Manganese ores likewise 

ae , S 
“\ a w WS ix <& 
‘S SSG MS QQ NSS X WN Ss. WX LON 
090 9 Sch. 
Fic. 85.—SECTION ACROSS THE ORE-BEARING ROCKS OF HiiTTENBERG IN 
CARINTHIA. (After F. Seeland.) 
sch, schistose rocks ; 7, limestones ; 0, bands of iron-ore.: 
occur under similar conditions in Sweden, Bukowina, Brazil, 
and the United States of N. America. 
I—EPIGENETIC ORE-FORMATIONS 
The formations included under this head are of later age 
than the rocks with which they are associated or in which 
they occur. They have been subsequently introduced into 
the positions they now occupy, and thus a large number 
appear in fissures and other cavities in rocks of all kinds, 
while in many cases they replace pre-existing minerals and 
rock-masses. ‘They may be grouped as fissure-veins or lodes, 
bedded veins, and irregular formations. This is not a very 
satisfactory classification, for one and the same ore-deposit 
may assume many different forms in its course, appearing 
sometimes as a “lode,” sometimes as a “bedded vein,” or as 




