Hardness of water occurs due to the presence of all of the following except:
Ref. Foundations of Community medicine. Page. 46
 
Hardness of water:

Temporary hardness is a type of water hardness caused by the presence of dissolved bicarbonate minerals (calcium bicarbonate and magnesium bicarbonate).  
Permanent hardness is caused by dissolved calcium sulfate (which is not removed by boiling).
Calcium bicarbonate
Magnesium bicarbonate
Calcium sulfate
Magenesium Oxide