4. What is the character of tungsten deposits?

There are three main geological settings of Tungsten deposits:

 
  1. Sheeted vein deposits -  The world's largest tungsten deposits are mostly of this type. Wolframite and less commonly scheelite occur in a number of sub parallel, narrow subvertical quartz veins separated by unmineralised rock above or within the upper zones of granite intrusions. The grade of tungsten within the quartz veins is typically around 1% WO3 in this type of deposit, but when the barren rock between the veins is included, the bulk grade of the system is typically about 0.2% WO3.
  2. Skarn deposits - where granites are intruded into limestones and tungsten-bearing fluids from the granites have reacted with the limestone to deposit scheelite. Skarns are typically somewhat higher grade but tend to be an order smaller in total tonnes than sheeted quartz vein tungsten deposits.
  3. Pegmatites - very coarse segregations/concentrations of specific minerals at the margins of granites.