Duplicate validity

A duplicate only measures what it repeats. Break the repeatability conditions and the pair silently stops measuring precision at all — Simón's list of practices that void a duplicate:

• different crews, sampling methods, or intervals; long time gaps;
• taking the duplicate from the last split instead of the first;
• not inserting the duplicate in the same batch as the original;
• a different analytical method, aliquot size, or detection limit;
• sending original and duplicate to different labs (that's a check assay, a different tool);
• relabelling coarse-reject re-pulps as "pulp duplicates" — that converts an analytical-precision measure into a sub-sampling measure without telling anyone;
• inserting only one duplicate type — pulp-only makes field and sub-sampling error invisible.

One genuinely contested point: field duplicates from quarter core. Simón describes it as the standard workaround; Bishi calls it "not recommended… biased sampling." Know which side your project's protocol takes.

In geoDB

geoDB records each duplicate's type (field/coarse/pulp/lab) and links it to its parent sample — the type decides which tolerance it is judged against, so log the type truthfully: a coarse-reject re-pulp is a coarse duplicate, not a pulp duplicate, even though it arrives as a pulp. geoDB does not (and largely cannot) verify the field-side conditions — same batch, same method, first split — those live in your sampling protocol.