Where records come from
The core catalog is built from the U.S. Geological Survey Mineral Resources Data System (MRDS) and related public mineral-resource fields. Community members may later submit verifications, flags, condition reports, photos, and new underground mine submissions.
Catalog eligibility vs confirmation
A record can be catalog-eligible because source evidence documents underground workings, while still remaining unconfirmed because UndergroundMines has not independently verified it. Eligibility is not the same as verification.
Public confirmation buckets
- Independently confirmed — member/admin verification or approved independent organization/source confirmation (including AZGS multi-source confirmation).
- Source-corroborated — additional historical mapping/source corroboration that does not meet the independent-confirmation definition.
- Awaiting independent verification — catalog-eligible but not yet independently confirmed or source-corroborated under the rules above.
No narrative history is invented for MRDS-only records. Structured facts and source cards are shown instead.
How USGS source data is interpreted
Fields such as work type, operating type, and development status are preserved as source values. We do not invent shafts or adits when the source only says “Underground.”
Why many records are unconfirmed
Independent verification requires member or admin confirmation with documented evidence. Most historical source records have not yet received that second layer of review.
Community verification and flags
Members can verify mines they already know or can document, or flag incorrect listings. Travel is never required. Visiting abandoned mines solely to verify listings is discouraged.
Exact community locations
Community-submitted exact coordinates default to private to the uploader. Public and free map views may show privacy-offset approximate areas. Explorer Pro may see exact community locations only when the contributor allows and administrators do not restrict disclosure.
Privacy-offset markers
Where privacy offset applies, map markers intentionally do not show the true coordinate. The marker communicates an approximate area, not a surveyed pin.
Updates and revisions
Moderation can merge duplicates, change confirmation status, or remove ineligible records. Removed false-positive records remain unavailable (HTTP 410) and are excluded from search, sitemaps, and related-mine suggestions.
California official sources
USGS MRDS provides the initial historical mineral-resource records used for catalog eligibility.
California DMR Mines Online (Department of Conservation / Division of Mine Reclamation) provides state mining-operation and reporting records via the official ArcGIS FeatureServer. A DMR match means California has/had a corresponding state mining record — it does not automatically prove underground workings. Operation type is interpreted carefully; only explicit underground operation values support underground corroboration.
USGS Prospect and Mine Related Features (DOI 10.5066/P9TAALR6, CC0) provides historical topographic map symbols. Only explicit underground feature types (for example Mine Shaft, Adit, Air Shaft) can support corroboration. Prospect pits, quarries, open pits, dumps, and placer symbols do not qualify as underground evidence. Historical mapped features may no longer exist in the field.
MRDS and the topo feature dataset are both USGS products; their combination is treated as map/source corroboration, not independent multi-organization confirmation, unless California DMR underground evidence is also present.
Nevada official sources
NBMG Active Mines and Energy Producers (OF2025-01) provides current/recent operation context. An active-mine match can enrich operator and commodity context; it does not automatically confirm underground workings.
NBMG mining districts supply district names/IDs that can be linked to UndergroundMines district entities without overwriting MRDS district provenance.
Nevada Division of Minerals AML is high-value physical evidence when precise shaft/adit openings are published. As of this phase, NDOM Open Data does not expose a public statewide precise AML openings layer suitable for coordinate matching, so UndergroundMines does not import or invent AML point locations.
USGS historical topo mine-feature symbols remain the primary physical mapped-working evidence for Nevada in this phase.
Arizona official sources
Arizona Geological Survey / ADMMR historical mine files (via the official AZGS Library metadata API used by mininginfo.azgs.arizona.edu) provide document titles, abstracts, licenses, and collection identifiers. High-confidence document matches with explicit shaft/adit/level language can create structured workings citations. Full copyrighted reports are not republished — metadata, compliant excerpts, and official links only.
USGS MRDS + AZGS historical underground documentation can constitute independent multi-organization confirmation when identity matching is extremely strong. USGS MRDS + USGS topo alone remains map/source corroboration.
Historical photographs are stored as rights metadata first. Images are not bulk-downloaded or displayed as reusable unless license metadata clearly allows it.
Mindat cross-reference
Mindat (via the official Mindat API — never scraped, and photographs are never imported) is cross-referenced against the existing catalog by name, aliases, state/county geography, and coordinates where both sides have usable coordinates. A match is scored across several independent signals and sorted into HIGH confidence, possible, ambiguous, or no match; a match is never treated as underground confirmation by itself.
Underground evidence is only recognized when the locality's own type or description explicitly documents physical underground development (shaft, adit, drift, level, stope, winze, raise, or similar) — not merely because the name contains "Mine" or minerals are reported there. Every accepted relationship and every automatic evidence-based confirmation is reviewed by an admin before it affects a mine's public confirmation status or appears as a public source.
Mindat is also searched for underground mines that do not yet exist in the UndergroundMines catalog. Candidates are cross-examined against internal MRDS, USGS historical topo features, and state records before being queued for admin review — a Mindat locality never becomes a public mine page until an admin accepts it with documented underground evidence and a completed duplicate check.