"Weathering" categories:
	
A:  Minor rustiness; rust haloes on metal particles 
     and rust stains along fractures are minor.
B:  Moderate rustiness;  large rust haloes occur on 
     metal particles and rust stains on internal 
     fractures are extensive.
C:  Severe rustiness;  metal particles have been 
     mostly stained by rust throughout.
E:  Evaporite minerals visible to the naked eye.