More complete is an open system, namely, in its simplest form,

  
    
      
        R
        
          
            →
            
          
        
        A
        
          
            →
            
               
               
              p
              (
              S
              )
               
               
            
          
        
        B
        
          
            →
            
               
               
              q
               
               
            
          
        
        ,
      
    
    {\displaystyle R{\xrightarrow {}}A{\xrightarrow {\ \ p(S)\ \ }}B{\xrightarrow {\ \ q\ \ }},}
  
where R stands for the rate of production of A, p(S) is the activation rate coefficient explicitly expressing its dependence on the stimulus intensity S and q represents the rate coefficient of removal from the state B.
Occurrence
Calcium chloride occurs as the rare evaporite minerals sinjarite (dihydrate) and antarcticite (hexahydrate). Another natural hydrate known is ghiaraite – a tetrahydrate. The related minerals chlorocalcite (potassium calcium chloride, KCaCl3) and tachyhydrite (calcium magnesium chloride, CaMg2Cl6·12H2O) are also very rare. So is true for rorisite, CaClF (calcium chloride fluoride). See also
Calcium(I) chloride
Calcium chloride transformation
Magnesium chloride

References
Greenwood, Norman  N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8. External links

International Chemical Safety Card 1184
Product and Application Information (Formerly Dow Chemical Calcium Chloride division)
Report on steel corrosion by chloride including CaCl2
Collection of calcium chloride reports and articles
Calcium chloride, Anhydrous MSDS
Difusivity of calcium chloride
Centers for Disease Control and Prevention, National Institutes of Occupational Safety and Health, "Calcium Chloride (anhydrous)"