Geoscience Reference
In-Depth Information
11
Resource Model Validations
and Reconciliations
Abstract
Mineral resource estimates are based on many interdependent and subjective decisions.
There is a need to check the fidelity of the models with the available data, ensure that the
models are internally consistent, and validate the models with production data if such data
is available. This Chapter discusses some commonly used techniques for model validation.
11.1
The Need for Checking and Validating
the Resource Model
of the model. In addition, there may be internal or external
factors that contribute and determine the need for additional
checking and validation of a resource model, including the
participation in this process of independent auditors. Al-
though the motivations may be different, the validation and/
or due diligence process is similar in all cases. Increasingly,
the mining industry prudently requires and emphasizes vali-
dation and due diligence work on resource models (François-
Bongarçon
1998
; Vaughan
1997
).
An internal or external due diligence is sometimes re-
quired by the project owner(s) because there is a need to en-
sure that the model is reliable and provides enough details
to make key investment decisions, such as acquisitions or
development decisions. An external due diligence or audit
is triggered when external financing is sought to develop or
acquire new mining assets.
The level of detail required to adequately validate the
model is also related to the level of detail of the resource
modeling itself and its objective. Determinant factors may
include the development stage of the project and the possible
due diligence or audit requirements.
There are many important reasons that mandate the need for
checking and validating resource models. The validation of
the resource model has two basic objectives: (a) to ensure
the internal consistency of the models, and (b) to provide, if
at all possible, an estimate of the accuracy of the model with
respect to the predicted variables.
Internal consistency means that all processes that result in
a resource model have been executed as intended, and that
there are no inconsistencies, explicit errors, omissions or
other factors that cause the model to deviate from what was
intended. The model should be a fair representation of the
available data. To ensure this, checks must be completed at
every step of the modeling process, including the assay and
composite database, topography, drill hole locations, down-
the-hole surveys, geologic coding, geologic interpretation,
block model development, grade estimation and resource
categorization.
An accurate model is one that reproduces well the ac-
tual tonnages and grades mined. This check can only be
performed if the mine is operating. Production data may
be used to calibrate and improve future updates of the re-
source model. However, the process is far from simple, as
there are multiple complications and potential pitfalls that
are discussed later in this chapter.
The motivations for validating the resource model stem
from different sources. In all cases, a minimum number of
checks should be performed to ensure that the model is ad-
equate and performing as expected, regardless of the purpose
11.2
Resource Model Integrity
When discussing the integrity of the resource model, it
should be kept in mind that there are a large number of steps
and processes that contribute to a resource model; every one
of them should be checked to ensure that the final product is
reasonable.
