Epilogue - Thanatia: The Destiny of the Earth's Mineral Resources - page 502

both, mining and chemical criticalities which is why mixing must be avoided when-
ever possible. The third relates to absolute scarcity. This is the worst scenario and
is the case of the precious metals. Contrarily to abundant elements such as iron or
aluminium, concentrating grams of precious elements would need vast amounts of
exergy. Exergy replacement cost is thus greater for critical elements than it is for
those found in abundance.
It provides an objective value to dispersion and offers a “natural” cost of minerals
extracted throughout the planet. Moreover, as exergy cost is additive, it can be
summed cumulatively, thus providing a tool for the systematic accounting of all
the mineral endowment extracted from Earth over a determined time period. It
also permits an assessment as to the impact of future scarcities, since declining
high-grade deposits will intensify replacement costs.
It should be remembered that the exergy replacement cost is not an embodied
exergy since it is calculated using an imaginary process from Thanatia to the actual
mine, instead of from the mine to the consumer. Note also that the replacement
cost does not enter into judging scarcities. No matter the amount of minerals that
remain unexploited or yet to be discovered, this parameter may indicate the annual
loss of mineral wealth rather than the absolute value of mineral endowment. This is
because for its calculation it only requires the quantity and ore grade of the mines
that are currently extracted and the Crepuscular Earth model.
Notwithstanding, should the physical details of the reserves be available, exergy
can also be used to evaluate mineral resources as a continuous, quantitative and
objective function of the tonnage, composition and concentration. This is done with
a unified unit of measure instead of the discrete and qualitative methodology of the
United Nations Framework Classification for Fossil Energy and Mineral Reserves
and Resources 2009 (UN, 2010).
Summarising, any raw material will have two components in its backpack: one
is the overall impact of its extraction and the other, the generated debt passed over
to future generations in failing to avoid dispersion. Any resource assessment must
be physically, not economically based.
Obviously, this also means that the current market prices of mineral commodities
should increase so as to include replacement costs and reach a stabilised value no
matter their current ore grade.
17.2.7 The thermodynamic rarity of minerals indicate the hidden
and real costs associated with production
The Webster Dictionary defines rarity as “something that is valuable because there
are few of its kind”. Rarity value therefore relates to the di culty in attaining some-
thing. In the case of a mineral deposit, rarity is associated with the improbability
of finding and accessing it. Once accessed, it also relates to the effort of isolating it
from undesired impurities considering environmental conditions and the availabil-
ity of water, energy and resources in general for its supply to market. Rarity thus
prescribes the character of a natural resource to a given mineral deposit.