[1.7.2]Pickaxe efficiency vs Redstone ore and Obsidian

I'm creating an extra pickaxe, what the strength and efficiency of an Iron pickaxe, and I noticed that it is slower at mining redstone than an Iron pickaxe. When I looked in the code I found this code:

    public boolean isToolEffective(String type, int metadata)
    {
        if ("pickaxe".equals(type) && (this == Blocks.redstone_ore || this == Blocks.lit_redstone_ore || this == Blocks.obsidian))
            return false;
        if (harvestTool[metadata] == null) return false;
        return harvestTool[metadata].equals(type);
    }

In the Block.class file. How is the iron pickaxe getting around this part of code? By all means as far as I can tell the Iron Pickaxe should be slow as well. Does anyone have any ideas? Redstone (and if this is the code causing the problem, obsidian also) is the only block that my pickaxe is slower than the Iron pickaxe on.