There are 2 basic types of natural fractures that need to be studied when characterising naturally fractured reservoirs - whether it be a geothermal or hydrocarbon reservoir. These are extension and shear fractures.
A variety of recent and old structures can be found on the karst limestone blocks of the Natih Formation, Oman. These include solution enhanced joints, Rillenkarren and tension gashes.
Veins are useful indicators of the sense of shear - here we look at some calcite veins in limestone in Oman which have a sigmoidal geometry in places and indicate a sinistral sense of shear.