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Property Plant Equipment and Mineral Rights and Reserves
12 Months Ended
Dec. 31, 2011
Property Plant Equipment and Mineral Rights and Reserves [Abstract]  
Property, Plant, Equipment and Mineral Rights and Reserves
(5)  
Property, Plant, Equipment and Mineral Rights and Reserves

Property, plant, equipment and mineral rights and reserves consisted of the following:

   
December 31,
 
   
2011
Restated
  
2010
Restated
 
Mineral rights and reserves
 $52,482  $65,018 
Land
  12,103   10,875 
Buildings and improvements
  97,503   86,410 
Machinery and equipment
  362,043   350,952 
Construction in progress
  25,207   15,285 
    549,338   528,540 
         

The range of useful lives to depreciate plant and equipment is as follows:

 
Buildings and improvements
3-50 years
Machinery and equipment
1-25 years
 
Depreciation and depletion were charged to income as follows:

   
2011
Restated
  
2010
Restated
  
2009
Restated
 
Depreciation expense
 $35,036  $30,106  $28,932 
Depletion expense
  2,574   1,180   883 
    37,610   31,286   29,815