Vein deposits of gold and silver are formed by igneous intrusion, and magma that cools slowly deep below the surface produces coarse-grained intrusive igneous rocks. Given these facts, when do vein deposits of gold and silver form among the following options:
- When magma warms up
 - flow of electrons
 - it can be seen
 - permineralization
 - When magma cools
 - aqueous solution
 - When the air is cold
 - When water rises


 

     When magma cools    