Grade Type

When quantifying the contained metal, a Grade Type Hierarchy influences the grade values used: The three grade types: Assay, Estimate and Survey form a hierarchy in which the Assay grade type has the highest priority, Estimate has second priority and Survey has the lowest priority.

Assay

Grades which result from a closely-spaced sampling programme undertaken prior to mining. These results are usually taken as the definitive grade value of each block.

Estimate

Grades interpolated from wide sampling programmes undertaken during the evaluation stage of the project.

Survey

Grades derived when the intermediate location was surveyed.

The grade value of a primary location is associated with the material mined at that location throughout the production process.

Grades are entered in the following order:

  1. Estimated grades prior to mining a location.

  2. Assayed results when they become available.

The estimated and assayed grades must be entered against a date - time which is prior to any material movements from a primary location.

When working in Reconciliation, the grade type must be defined with a unit of measure that is either in parts per million (ppm) or a percentage value (%).

Parts per million (ppm)

The contained metal value is calculated in international troy ounces (ozs or t ozs):

Where:
1 troy ounces = 31.1034768g.
and where:
Material = (Quantity x Grade ) x 31.1034768

Percent (%).

The contained metal value is a percentage of the quantity.

Where:
Material = (Quantity x Grade) / 100

The unit of measure for a grade type is defined in Reference Data.

Configuration

Grade types are defined in Reference Data using Groups | Materials Management | GradeType. How and when the ore was sampled will determine the grade type.

In order to define a grade type you must specify:

  • Code = Assay, Estimate or Survey.
  • Description = A site - defined name for the grade type.
  • Abbreviation = A site - defined abbreviation for the grade type.

For example, you could define a grade type as follows:

General Type
Code ASSAY
Description Fire Assay Au
Abbreviation Fire Assay Au