Simply depends on the price of copper in the market place.

And the costs of extraction.

Threshold value is function of so many factors; staring from the location/country of the deposit; mineralogy , process selected for maximum recovery at a grade aimed, tailing disposal etc.etc in addition to forward integration. So a general question like that would be difficult to answer.

Yes, it all depends on the market as alluded by Mr Rao and Rawle. You can estimate it from the following Cutoff grade formula:

• CoG = m/(p-s) x r where
• m is the milling cost ($/t)
• p is the sale price of the commodity ($/t) 
• For different commodity prices refer to Metal-Prices-in-the-United-States.pdf
• s is the sales cost (i.e. refining and marketing) ($/t)
• r is the process recovery (%)

Here is an example:

Estimate the unit profit of mining and cut-off grade of a copper ore body with 0.82% of copper, if the selling price of copper in the concentrate is $1.63/kg. Assuming that the overall cost of mining and processing is $7.50/tonne and grade of Cu in tailings is 0.07%.

Solution:

Recovery = (Feed – tails grade)/feed grade = (0.82-0.07)/0.82 = 92%

Gross Value = Grade x Recovery x Price x Conversion Factor

Thus,

Gross Value = 0.0082 x 0.92 x 1.63/kg x 1000 kg/tonne

= $12.29/tonne

CoG = Cost/[Price x Recovery]

• = ($7.50/tonne)/ ($1.63/kg) x (0.92)
• = 4.2 kg/tonne or 0.42% Cu by weight

Therefore,

• Profit = Gross value – cost
• = 12.29 – 7.50= 4.8$/tonne

Good example and may give an indication based on the mathematical equation; still too many assumptions on cost of processing/recovery etc.

All of those above have opinions expressed are correct and beneficial to such a general question. The price of copper in the market place is very critical and the mineralogy . Industry have gone through different and diversified transformation and the right understanding is needed to estimate cost of production which involves different and diversified functions . Go to onemine and type your question more specifically and a lot of information would be available.

I agree! Mineral exploitation is more complex, not in understanding what to do and how to do, but the parameters required are quite a few and there are no thumb rules. The economics may keep on changing depending on not only the market price of the metal but also the variations in ore characteristics, more stringent environmental issues etc.

We need more understanding and expertise.