Ore Waste Discrimination
This function classifies blocks as ORE or WASTE according to cutoff and minimum thickness criteria supplied by the user and applied to columns of blocks in the model.
To run this function: Choose Block model > Column processing > Ore/Waste discrimination, or...
To facilitate the explanation of the discrimination process it is necessary to introduce a couple of terms.
A band is a contiguous set of blocks whose grades are either all below cutoff or greater than or equal to cutoff. Bands are not subject to minimum width criteria.
A layer is a band whose width meets or exceeds a given minimum and is thus classifiable as ORE or WASTE.
The process first identifies all of the bands in the column and classifies those that meet the minimum width criteria as ORE or WASTE. Unclassified bands that remain will fall into one of three groups:
- A sequence of bands whose aggregate width is less than the minimum and is bounded by layers of the same class.
If the composited grade of the unclassified bands has the same relation to the cutoff as the surrounding layers then the unclassified bands are classified as the same class as those layers.
For example, if the composite grade is less than cutoff and the surrounding layers are WASTE, the unclassified bands are classified as WASTE. Otherwise, if the surrounding layers are ORE, the lowest grade composite that comprises either the layer above with the unclassified bands or the layer below with the unclassified bands is classified as WASTE.
Conversely, if the surrounding layers are WASTE, the highest grade composite that comprises either the layer above with the unclassified bands or the layer below with the unclassified bands is classified as ORE.
- A sequence of bands whose aggregate width is less than the minimum width and are bounded by layers of different classes.
The two upper and two lower bands of the unclassified interval are composited and the composites are classified depending on the composite grades.
- A sequence of bands whose aggregate width is greater than or equal to the minimum.
A window with a width at least that of the minimum is moved over the interval. If the specified objective is to maximise ore volume then the blocks in the window whose composite grade is greatest are classified as ORE or WASTE depending on that grade. If the specified objective is to maximise ore grade then the blocks in the window whose composite grade is least are classified as ORE or WASTE depending on that grade. If the specified objective is to maximise contained product then the blocks in the window whose composite grade differs most from the cutoff grade are classified as ORE or WASTE depending on composite grade.
After an unclassified interval is classified, the process is repeated until all blocks are classified as ORE or WASTE.
Digging Zones
Digging zones allow for the specification of different thicknesses for ore and waste depending on where we are in the column. The determination of digging zones follows different rules for different mining strategies. The upper digging zone will always be the first band in the column.
Select the mining method to use to determine digging zones. This may be
- None, no digging zones
- Truck & Shovel
The lower digging zone will be the last band in the column.
- Dragline
The lower zone will comprise all bands that lie below a given depth.
The middle zone will be all other bands.
Depth to lower digging zone
If `Dragline' is selected for Digging Zones then the depth from the top of the column to the lower digging zone must be entered.
Maximise
Select the property to maximise when resolving thick, unclassified intervals. This may be:
- Contained Product
- Ore Volume
- Ore Grade
See above for the application of this value.
Minimum thicknesses
Supply the thicknesses which intervals must meet or exceed for them to be classified as ORE or WASTE. If digging zones have been specified, thicknesses must be specified for each zone.
Attributes to composite (list master first)
Attribute
Select a numeric attribute to composite. The first attribute in this list will be the master attribute whose value relative to cutoff will determine possible ORE and WASTE classifications. Any negative value for this attribute will be treated as zero.
Composite
Select or enter an attribute in which to store the composited values. If the attribute does not exist, it will be created with a background value of -1.0. Leave this field blank if you do not wish to store a composite value. If an existing attribute is selected, it must be of real type.
The classification parameters are divided between two tabbed regions on the form, the Standard tab and the Advanced tab. The parameters on the Standard tab of the Block model ore/waste discrimination form are described below:
Standard:
Cutoff
Enter the value which the master attribute value for a block or interval must meet or exceed for that block or interval to be classed as ORE or possible ore.
Ore attribute
Select or enter the name of an attribute to store the ORE and WASTE flags. If the attribute does not already exist it will be created with a type and background value appropriate for the ore and waste values given subsequently.
Ore Value
Enter the value that will signify ORE blocks. If an existing ore attribute was selected, this value must conform in type to that attribute.
Waste Value
Enter the value that will signify WASTE blocks. If an existing waste attribute was selected, this value must conform in type to that attribute.
Direction of columns
Select the direction which will define the orientation of columns in the model. This may be X, Y, Z -X, -Y or -Z. The directions which may be used include:
- -X, The columns are horizontal and aligned with the X axis of the block model and are processed in order of maximum X to minimum X value.
- X, The columns are horizontal and aligned with the X axis of the block model and are processed in order of minimum X to maximum X value.
- -Y, The columns are horizontal and aligned with the block model Y axis and are processed in order of maximum Y to minimum Y value.
- Y, The columns are horizontal and aligned with the block model Y axis and are processed in order of minimum Y to maximum Y value.
- -Z, The columns are vertical and are processed in order of maximum Z to minimum Z value.
- Z, The columns are vertical and are processed in order of minimum Z to maximum Z value.
Constrain discrimination?
Select `Yes' if you wish to constrain the discriminated blocks.
The parameters on the Advanced tab of the Block model ore/waste discrimination form are described below:
Advanced:
Secondary attribute
Select or enter the name of the attribute which will store the secondary classification. If you leave this field blank, no secondary classification will occur. The secondary attribute will be populated from the values defined in the Value column of the Classification table on the form. The values in the Value column can be integers or characters, and the appropriate attribute will be created if the selected secondary attribute does not already exist.
Dilute ore classes?
Tick this box if you wish to add external dilution to the top and bottom of each ore interval. A block that contains any dilution will be marked as External Dilution in the secondary attribute, and the percentage of the block included will be in the percentage attribute.
Dilution thickness
Enter the thickness value (as a distance) for the external dilution. This value cannot be greater that 0.5 times the minimum waste thickness enetered on the form. If you are using different zones, the dilution thickness cannot be greater than 0.5 times the lowest minimum waste thickness.
Percentage attribute
Select or enter the name of the attribute which will store the percentage value. The percentage value will vary form 0.0 to 1.0, 1.0 being 100 percent. All ore blocks will be given a value of 1.0. If the attribute does not exist, it will be created with a background value of 0.0.
Classification Values
The values in the Values column of the table are used to populate the Secondary attribute, when an advanced classification is performed. The values will be populated as follows:
- If the primary classification is ORE, and the master grade is greater than or equal to the cutoff, then the advanced classification will be the True Ore value
- If the primary classification is ORE, and the master grade is less than cutoff, then the advanced classification will be the Internal Dilution value
- If the primary classification is WASTE, and the master grade is greater than or equal to the cutoff, then the advanced classification will be the Ore Loss value
- If the primary classification is WASTE, and the master grade is less than cutoff, then the advanced classification will be the True Waste value
- The External Dilution value is used when the Dilute ore classes? option is chosen
The values in the Value column may be integers or character values. However, if you want the Secondary attribute to be of integer type, you will need to make ALL the values in the Value column integers.
Notefile name
Enter a name of a text file that will be created to hold information pertaining to this discrimination run.
Choose Apply to perform the ore/waste discrimination or Cancel to return to the BLOCK MODELLING menu.
Result
The selected blocks will be classified as ORE and WASTE and values of nominated attributes will be composited on discriminated ORE and WASTE layers and their composited grades stored in the model.