The metal value provides an idea of the potential profitability of a mineral project. By calculating the metal value and then deducting the estimated mining costs, you gain insight into the viability of bringing this mineral project into production at current metal prices.
An indication of the current mineral value of the rocks can be found using Kitco’s Rock Calculator. As seen in the image below, you can choose between different variables in the “Units/Weight” column, depending on how the drill results are reported (%, grams/tonne, ounces/tonne, and pounds/tonne).
You can click on the image link below, which will redirect you to the specific subpage on Kitco’s website:
As it depends on the mining company whether it reports its drill results in grams per tonne or ounces per tonne, remember the number 0.029, as you will need this to convert troy ounces into grams. On the break even analysis page, it is stated that 1 troy ounce equals 31.103481 grams per ton, which equals 34.2857 grams per tonne. Since 1 gram equals 0.0321492 troy ounces, the conversion factor is calculated as: 0.0321492 / 34.2857 x 31.103481 = 0.0291652 (rounded 0.029).
Thus, when a mining company reports a drill result of 0.145 ounces per tonne, you now know that this equals (0.145 / 0.029 =) 5 grams per tonne. Conversely, when a mining company reports a drill result of 10 grams per tonne, you now know that this equals (10 x 0.029 =) 0.29 ounces per tonne.
On the break even analysis page, there is also an explanation of how to convert a drill result reported in a percentage (%) to an amount in pounds (lbs) per tonne. You will find this explanation under the header “How to Calculate the Cut-Off Grade”, but in summary: 1% equals 22 pounds.
How To Calculate the Metal Value per Tonne
In the following table, I have created some examples for calculating the metal value, using the metal prices from March 23, 2012 from the Kitco image above.
|Drill Result||Calculation||Metal Value per Tonne|
|2% Copper||2 (percent) * 22 (percentage to pounds) * $3.82 (copper price per
|1.8% Nickel||1.8 (percent) * 22 (percentage to pounds) * $8.30 (nickel price per
|1.14 g/t Gold||1.14 (gram per tonne) * 0.029 (gram to troy ounces) * $1649.80 (gold price
|70 g/t Silver||70 (gram per tonne) * 0.029 (gram to troy ounces) * $31.67 (silver price per
Although mineral values are often expressed in tonnes, sometimes they are expressed by tons as well. As 1 ton equals 907.18474 kilograms and 1 tonne equals 1,000 kilograms, just remember the difference between tonne and ton is approximately 10% (mnemonic: less letters, lower outcome).
For more information on how to calculate the metal value of a deposit as a whole, I recommend you to read the mineral deposit value page as well. This will provide you with a comprehensive understanding of the process and various factors to consider when estimating the value of an entire mineral deposit.