Weighted-average-grade (WAG) Stockpiles
WAG Stockpiles with no Analyte Balancing
WAG stockpiles consider stacked and reclaimed quantity. If analyte balancing is not enabled, only stacked analyte quality is considered.
Example: A mine has the following stockpiles:
- MS-1—Mine Source stockpile 1 has Cu=25%, H2O=10% and has ABC Mining as a 100% contributor.
- MS-2—Mine Source stockpile 1 has Cu=20%, H2O=5% and has Diversified Mining as a 100% contributor.
- WAG—Run of Mine (ROM) stockpile starts with 0 tonnes of material.
- PROD—Production stockpile starts with 0 tonnes of material.
The following transactions take place:
- 5000 tonnes is stacked onto WAG from MS-1.
- 5000 tonnes is stacked onto WAG from MS-2.
- 7500 tonnes is reclaimed from WAG and stacked onto PROD.
The following table displays the transaction history of the WAG (unbalanced) stockpile.
|
Sequence |
Mass |
Balance |
Cu % |
Cu (t) |
H2O% |
ABC Mining |
Diversified Mining |
|---|---|---|---|---|---|---|---|
|
1 |
5,000.00 |
5,000.00 |
25.00 |
1,125.00 |
10.00 |
5,000.00 (100.00%) |
|
|
2 |
5,000.00 |
10,000.00 |
22.43 |
2,075.00 |
7.50 |
5,000.00 (50.00%) |
5,000.00 (50.00%) |
|
3 |
7,500.00 |
2,500.00 |
22.43 |
518.75 |
7.50 |
1,250.00 (50.00%) |
1,250.00 (50.00%) |
WAG Stockpiles with Analyte Balancing
WAG stockpiles consider stacked and reclaimed quantity. If analyte balancing is enabled, both stacked and reclaimed analyte quality is considered.
Important: Analyte balancing should only be used if accurate sample data is available for both stacking and reclaiming transactions.
Example: A mine has the following stockpiles:
- MS-1—Mine Source stockpile 1 has Cu=25%, H2O=10% and has ABC Mining as a 100% contributor.
- MS-2—Mine Source stockpile 1 has Cu=20%, H2O=5% and has Diversified Mining as a 100% contributor.
- WAG—Run of Mine (ROM) stockpile starts with 0 tonnes of material.
- PROD—Production stockpile starts with 0 tonnes of material.
The following transactions take place, and the material in each transaction is sampled:
- 5000 tonnes is stacked onto WAG from MS-1. Sampling returns values of Cu=23% and H2O=9.5%.
- 5000 tonnes is stacked onto WAG from MS-2. Sampling returns values of Cu=18% and H2O=6%.
- 7500 tonnes is reclaimed from WAG and stacked onto PROD. Sampling returns values of Cu=20.6% and H2O=7.5%.
The following table displays the transaction history of the WAG (balanced) stockpile.
|
Sequence |
Mass |
Balance |
Cu % |
Cu (t) |
H2O% |
ABC Mining |
Diversified Mining |
|---|---|---|---|---|---|---|---|
|
1 |
5,000.00 |
5,000.00 |
23.00 |
1,040.75 |
9.50 |
5,000.00 (100.00%) |
|
|
2 |
5,000.00 |
10,000.00 |
20.45 |
1,886.75 |
7.75 |
5,000.00 (50.00%) |
5,000.00 (50.00%) |
|
3 |
7,500.00 |
2,500.00 |
20.01 |
457.62 |
8.50 |
1,250.00 (50.00%) |
1,250.00 (50.00%) |
Analyte Quality Relevance on WAG Stockpiles
The relevance percentage indicates the proportion of a WAG stockpile's mass for which analyte sample values are known:
Relevance = Sum of transaction masses with known analyte sample values / Stockpile Mass
The relevance of analyte sample values displays in a tooltip over the analyte sample value on the Activity tab of the WAG Stockpile screen. The tooltip displays two values:
- The relevance of the sampled analyte value to the total mass of the WAG stockpile, and the sample result type. For example, a relevance of Rapid (50%) indicates that the analyte value entered via a Rapid sampling template is relevant to 50% of the stockpile mass.
- The percentage of the mass that has been sampled.
Impact of Relevance on WAG Calculation
A standard calculation of the weighted-average grade is:
Weighted Average = Sum (Analyte Value * Mass ) / Sum (Mass)
However, the calculation of the mass of analytes in WAG stockpiles includes the relevance of the analyte sample values. The formula used is:
Weighted Average = Sum ( Analyte Value * Mass * Relevance) / Sum ( Mass * Relevance)
Note: Billboards use the standard calculation of the weighted-average grade.
Example of relevance calculation: A stockpile has 100 t of coal. The stockpile has not been surveyed; therefore, the Ash value is unknown.
- A loading (stacking) transaction is made of 100 t of coal, which has been sampled at 10% Ash with 100% relevance. After the transaction, the stockpile has 200 t coal at 10% Ash with 50% relevance. The 10% Ash value is relevant to 50% of the total mass on the stockpile.
- A second loading transaction is made of 50 t of coal, which has been sampled at 10% Ash with 100% relevance. After the transaction, the stockpile has 250 t coal at 10% Ash with 60% relevance. The 10% Ash value is relevant to 60% of the total mass on the stockpile.
