


CHAPTER XVI 
ORE-FORMATIONS 
Syngenetic Ore-Formations—Native Metals and Ores in Igneous Rocks ; 
Ores in Bedded Rocks (Chemical Precipitates, Clastic Ores, Ores 
in Schists). Epigenetic Ore-Formations—Fissure Veins or Lodes; 
Nature of Fissures; Width and Extent of Lodes; Simple and 
Complex Lodes ; Transverse and Coincident Lodes; Systems of 
Lodes ; Branching and Intersection of Lodes; Heaving of Lodes ; 
Contents of Fissure Veins ; Structure of Fissure Veins ; Outcrop of 
Lodes; Gossans; Association of Ores in Lodes; Succession of 
Minerals in Lodes ; Walls of Lodes ; Stockworks. 
ORES are metalliferous minerals or mixtures of such minerals, 
in which the proportion of metal is often sufficiently large to 
admit of its being profitably extracted. The term “metal” is 
here used in a conventional (not in a chemical) sense, and does 
not, therefore, apply to the metals of the alkalies and alkaline 
earths, but only to the “heavy” metals of commerce, viz. : 
gold, silver, platinum, copper, tin, lead, zinc, iron, manganese, 
nickel, cobalt, chromium, mercury, antimony, bismuth, etc. 
Classification.—As one kind of ore-formation frequently 
passes into another, while considerable doubts obtain as to 
the genesis of many ores, it is hardly possible to devise a 
scheme of classification to which exception cannot be taken. 
For purposes of description, however, ore-formations may be 
srouped under these two main divisions:—i. Syngenetic or 
Contemporaneous, and 2. Epigenetic or Subsequent, 
I—SYNGENETIC ORE-FORMATIONS 
These are formations of the same age, broadly speaking, 
as the rocks in which they occur or with which they are 
immediately associated. Some of them appear in igneous 
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