Why drill?
Drilling is the only way to directly sample rock at depth, making it the definitive test of an exploration target. Diamond drilling, which uses a diamond-impregnated bit to cut a continuous cylinder of rock called core, is preferred for mineral exploration because it preserves the geology intact for detailed study.
Because rigs, crews, and assaying are costly, drilling is reserved for ranked targets that have already passed cheaper geochemical and geophysical screening. A first-pass program tests whether mineralization exists; success leads to systematic infill drilling.
Logging and sampling core
Recovered core is laid out in trays, photographed, and logged by geologists who record rock types, alteration, structure, and mineralization. Intervals of interest are split — typically half is sampled and half retained — and sent to an accredited laboratory for assay.
Quality control is built into the process. Certified reference standards, blanks, and duplicates are inserted into the sample stream so that laboratory performance can be verified, a practice required to support disclosure under NI 43-101.
Reading a drill intercept
A reported intercept gives a grade over a downhole length, for example a copper or gold grade over a number of metres. A crucial nuance is that downhole length is not the same as true width: if a hole cuts a mineralized zone obliquely, the intercept overstates the real thickness. Responsible disclosure states whether widths are true or estimated.
Single spectacular intercepts should be treated cautiously. Continuity between multiple holes, supported by geological understanding, is what ultimately determines whether mineralization can become a resource.
From core to resource
Once enough drilling defines continuity and grade, an independent Qualified Person may estimate a mineral resource. Drilling therefore sits at the heart of the path from target to resource, but a strong intercept is a beginning, not a conclusion.
This article provides general educational information about mineral exploration. For information concerning Eastfield's mineral projects, readers should refer to the Company's project disclosures, news releases and continuous-disclosure filings on SEDAR+.