Optimal Drill Spacing for Limestone Resource Classification (Inferred vs Indicated)
Hello everyone,
I am currently working on a limestone exploration permit in a sedimentary environment. Last year, we completed a first phase of test drilling on a selected reference area. We are now preparing a geophysical survey over two 1 km² blocks within a 6 km² zone of interest.
After the geophysics, I plan to run a drilling campaign with a relatively wide drill spacing. My objective is to generate at least Inferred Resources, and—if technically defensible—Indicated Resources, knowing that limestone for quarry operations does not usually require very tight drilling grids.
The drilling pattern I am considering is 300 m × 150 m.
Given that this is a massive, relatively continuous sedimentary unit (not a vein-type system), my question is:
Based on your experience, is a 300 × 150 m drill spacing sufficient to support the definition of Inferred Resources, and potentially Indicated Resources, for a limestone deposit intended for quarrying?
I would appreciate technical feedback, examples from similar projects, or references to best practices within JORC/NI43-101/CRIRSCO standards regarding spacing requirements for bulk industrial minerals.
Thank you in advance for your insights!