W. H. VON STREERUWITZ-GENESIS OF CERTAIN ORE VEINS. 
69 
the iron grew up in and with the veins, and reaching towards the surface 
formed the outcrops known by the name of gossan, almagres, eiserner 
Hut, etc. 
3. The fissures could be charged with veins in comparatively short 
time, since under the influence of heat and galvanic currents the growth 
of most of the metal salts is a very rapid one. 
4. Ore-bearing and barren quartz gangues are mostly not the product 
of igneous eruptions, but were formed from aqueous solutions in which 
the silica was gelatinized by acid gases, vapors or fluids. This explains 
the existence of larger and smaller ore pockets in cavities in the quartz 
formed by the ascending gelatinizing gases and filled by the growth of 
metal salts or by metallic vapors and solutions. It accounts also for the 
innumerable microscopic and larger cavities filled with gases and liquids, 
which hardly could have been retained in crystalline or amorphous pre¬ 
cipitations. 
5. Indisputable igneous phenomena in such silicious gangues are the 
result of subsequent igneous action. 
6. Alterations of the rocks next to such silicious gangues are not 
necessarily the result of igneous action, but can be caused by leaching as 
well as impregnation from the gangue. 
7. The formation of banded agates does not always take place in rock 
cavities by osmosis, but can also take place free in solutions, the growth 
progressing from a center outwards. 
