I am not fan of low grade copper mine unless it is in a developing country. I am not saying anything particularly for PMH. It might be a good company to invest after taking everything into account.
For example, at current copper price, the contained value for ore with 0.4% copper is about $25/t. The value is very miginal. Any cost increasing will put the operation in red.
Of course, the low grade copper project/mine is very sensitive to copper price. If the copper price is at $10,000/t, the ore is worth about $40/t.
For comparsion purpose, some kind iron ore worth $60/t, and thermal coal $50/t. Both of them require less mining process..