378 , F. L. Hess— Tactite. 



many places of commercial value for the introduced 

 metals — immigrants from the invading rock — including 

 gold, silver, lead, copper, bismuth, zinc, tungsten and 

 molybdenum. 



For the rocks of the complexly mineralized zone, I pro- 

 pose the name "tactite," derived from the Latin "tac- 

 tus," (touching). It is a word which will not, of course, 

 like granite and similar words, when used in a narrow 

 sense, mean a rock of a fairly definite composition, but 

 will be a class or group name like gneiss, schist, horn- 

 stone, porphyry, or lava. 



Tactite may be defined as a rock of more or less com- 

 plex mineralogy formed by the contact metamorphism 

 of limestone, dolomite or other soluble rocks into which 

 foreign matter from the intruding magma has been intro- 

 duced by hot solutions or gases. It does not include the 

 inclosing zone of tremolite, wollastonite and calcite. 



