Hi @Allgood83,It seems to me that it's the presence of liquid water that does the weathering (ice and humidity are not a problem).Brazilian Li districts have a wide range of rainfall.Many quarries have exposed the weathering horizon.A particularly interesting case of progressive weathering through rock fissures at 5m sub-surface (on a well drained hillside)is shown here ( ASX Ann pg 8 ) . Annual rainfall near this underground mine is around 33in/yr ( URL ). Visit ( map )GLTAH
