4 Iwasaki : 



nations of LI^x'OLx,^^ deposited between the ore-bringers and the- 

 preëxisting rocks, the latter of which obstructed the passage of the 

 emanations from the former. When the emanations force them- 

 selves into the fissm-es of the rocks and deposit heavy metals there, 

 we have mineral veins. When the magmatic emanations, by their 

 strong rush and chemical action, dissolve part of rocks, make 

 cavities of various forms, and deposit heavy metals therein, then 

 we have replacement deposits. Impregnations are the ore-bodies 

 disseminated in the rock-masses. 



3. The Order of Petrification of Emanations. 



Lincoln'^ has classified emanations into four groups, i. e., 

 actual, fossil, repressed, and potential emanations. '^ Actual 

 emanations may be observed as gases and vapours from lava 

 streams exi:>elled from volcanic vents." "Fossil emanations are 

 the more or less well-preserved remains and traces of actual ema- 

 nations. The complete preservation of past emanations is often 

 seen as inclusions in minerals, while partial preservation is com- 

 mon in druses and in lithophyses, at contacts and in veins." " It 

 is well to remiember in this connection that the mineral veins and 

 contacts frequently appear to be in whole or in part of magmatic 

 origin." 



As the emanations begin to get cool, the minerals begin to be 

 formed, and petrification occurs. From frequent observations, I 

 have come to the conclusion that the order of petrification of ema- 

 nations is similar to that of the formation of rock-forming minerals 

 in magma; for in both cases, the falling of temperature is the chief 

 agent in forming minerals from liquids or gases at high tem- 

 perature. The following list shows the order of petrification of 

 emanations observed in Japanese ore-deposits:—!, magnetite, 2. 

 chromite, o. hematite, 4. garnet, 5. augite and hornblende, 6. 

 scheelite, 7. pyrite, 8. cobaltite, 9. chalcopyiite, 10. barite, 11. 

 argentite, 12. gold, 13. quartz, 14. tetrahedrite and enargite, 

 15. calcite. The minerals at the head of the series are those 



1) Lincoln : Economic GcolOffij, Vol. II., No. 3, ix 258, 1907. 



2) Loc. cit. 



