Check vanilla ores like diamond or coal. 
 
  
I found this piece od code wich i found in BlockRedstoneOre.java.patch  
public void dropBlockAsItemWithChance(World p_149690_1_, int p_149690_2_, int p_149690_3_, int p_149690_4_, int p_149690_5_, float p_149690_6_, int p_149690_7_) 
    { 
        super.dropBlockAsItemWithChance(p_149690_1_, p_149690_2_, p_149690_3_, p_149690_4_, p_149690_5_, p_149690_6_, p_149690_7_); 
    } 
  
    {{{{{    if}}}}}} (this.getItemDropped(p_149690_5_, p_149690_1_.rand, p_149690_7_) != Item.getItemFromBlock(this)) 
    private Random rand = new Random(); 
        private Random rand1 = new Random(); 
            @Override // World, meta, fortune 
            public int getExpDrop(IBlockAccess p_149690_1_, int p_149690_5_, int p_149690_7_) 
            { 
                if (this.getItemDropped(p_149690_5_, rand, p_149690_7_) != Item.getItemFromBlock(this)) 
                 { 
                    int j1 = 1 + p_149690_1_.{{{{{{{{rand}}}}}}.nextInt(5); 
                    return 1 + rand.nextInt(5); 
                 } 
                return 0; 
             } 
  
  
i just copyed it and it gives me errors 0.0  i have marked the errosrs in these things {{{{{{ }}}}}} not that i dont know java i'm just not experienced enough to find the problem .