Surpac Tips & Tricks: Simple Reblock and dilution of grade


When working with block models, whether you’re a geologist or mining engineer often circumstances arise where the block size needs to be changed, for example to better represent the selective mining unit (SMU). Within GEOVIA Surpac software this can be done using a variety of methods, such as the Simple reblocking function or the Block Model Converter (BMC). Many users are not familiar with how these functions work or how to use them. In this post we will look at the Simple reblocking function and in detail how grades change between block sizes for managing dilution.


Workflow: Simple Reblocking

This function will reblock a block model to a chosen block size, typically to a block size that is larger than the blocks in the input model. If this is the case, then the attribute values from the smaller blocks are used to calculate the attribute values for the large block.

1. Open GEOVIA Surpac 6.9 or older.
2. Drag and drop a MDL block model into the graphics window to open it.
3. Go to Block Model > Block Model > Simple Reblock




4. In the form above:

• Enter your output block model name and the description (description optional).
• Select the type of reblocking, Standard or Advanced (Standard for regular blocking, advanced for variable blocking). Advanced Reblocking gives you much more flexibility, but will be much slower than Standard Reblocking.
• Define the new user and sub-block sizes.
• Choose which attributes will be included and their reblocking method. See details on each reblocking method by pressing on the ? icon to access Surpac help.
• Select an SG attribute, if desired. The SG attribute controls the weighting, if left blank by default weighting is performed by volume, whereas if an SG attribute is selected then weighting is performed by tonnage.


Click Apply to reblock the model.

5. After the reblocking is complete, remember to save the new reblocked block model:


The results:


Input BM: User block size: 4x4x4



Output BM: User block size: 8x8x8


Grade assigned to reblocked model applied a volume weighted average. For example, for the selected block above:



The same result can also be seen on the sub-blocked input block model:



Input BM:

User block size: 8x8x8
Sub block size: 4x4x4




Output BM: User block size: 8x8x8



The above study shows simple reblocking is an effective and easy to use method for reblocking a block model in GEOVIA Surpac software. The ability to select the reblocking method and SG attribute provides the user with the flexibility and tools to weight by tonnage or volume, if desired and control how negative background values are treated.