corundum 

  1. 名詞
不可數名詞: 剛玉, 金剛砂

    
                        
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例句

                

                    
    
                                                    
  1. 
                                Rub the diamond on corundum sandpaper.                            
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  2. 
                                Ruby is the only corundum that has its own name.                            
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  3. 
                                When transparent and clear, corundum is used as a gem.                            
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  4. 
                                Heating the hydroxides leads to formation of corundum .                            
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                                Corundum that contains ~0.01% of titanium is colorless.                            
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