Historical and legacy data
Old drilling and estimates can save years and millions of dollars, but they must be verified before anyone relies on them.
2 min read
Historical data is exploration work done by earlier owners, often decades ago. It can be very valuable, but it cannot be relied on until it has been checked.
What it is
Many projects were explored before, sometimes by major companies, and then dropped because of low prices, remoteness or corporate changes. What they left can include drill logs, assays, stored core, maps, geophysical surveys and resource estimates. Data like this can save years of work and millions of dollars.
The problems with it
- Unknown quality control: old programmes often have no records of standards, blanks or duplicates.
- Old methods: older laboratory methods and detection limits may differ from today's.
- Missing data: logs, assays or core may be lost or incomplete.
- Location errors: old collar positions may be on local grids that are hard to match to modern coordinates.
- Non-compliant estimates: estimates made before modern codes used different categories, prices and cut-offs.
Historical estimates
A is a resource estimate made before, or outside, a current . Codes allow it to be disclosed only with clear warnings: who made it and when, the categories used, the key assumptions, and a statement that a qualified person has not done enough work to treat it as a current resource.
How it is verified
| Step | What it checks |
|---|---|
| Compiling and digitising records | That the data is complete and consistent |
| Locating old collars | That holes are where the records say |
| Re-logging stored core | That the geology was recorded correctly |
| Re-assaying old core or pulps | That the original grades can be reproduced |
| That new drilling beside old holes gives similar results | |
| New quality control | That all new work meets modern standards |
If the checks pass, the historical data can be used in a new estimate under a current code.
Why it matters
Verified historical data can carry a project forward by years and save much of the cost of new drilling. Unverified, it is a hint of potential, not evidence. The cost and time of verification belong in any plan built on old data.
Ranges are indicative and vary by deposit and region. This is educational material, not investment advice.
Key terms
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Educational material only. Nothing here is investment advice or an offer to buy or sell any security or mineral interest.