6. Cost of sales
 
  2018 
US$’000 
  2017 
US$’000 
 
Mining 105 376   96 005  
Salaries and wages 15 124   12 467  
Utilities 10 319   9 495  
Diesel 650   705  
Materials and consumables 650   8 274  
Re-agents 4 471   3 653  
Steel balls 6 715   6 757  
Overhead 4 117   8 055  
State royalties 2 916   1 665  
Depreciation – property, plant and equipment 29 008   16 476  
Cost of commodities 18 644   4 241  
Impairment and write off of property, plant and equipment 3 630   –  
Change in inventories – finished products and ore stockpile 3 781   (1 582)  
Total cost of sales excluding selling costs 215 925   166 211  
Selling costs 58 453   46 290  
Freight services 23 404   14 288  
Cost of sales 297 782   226 789