Where the facts come from
Every page on this site draws on exactly two data layers, and it never blurs them.
Layer one: the historic mineral record
The mineral-history sections summarize the USGS Mineral Resources Data System (MRDS), a public-domain federal database of 265,790 historic mines, prospects, and mineral occurrences across the fifty states. MRDS is a legacy database: the USGS stopped updating it, and the copy we summarize was last revised August 2022. That is fine for what we use it for — the geology it records didn't move — and every page that cites it says so.
We publish MRDS as counts and county clusters only — never as a list of named historic sites with coordinates. That is deliberate:
Mineral history, not an invitation. This mineral history comes from a federal record of historic mines, prospects, and occurrences. It is not a list of places to collect. Historic mine sites are usually on private land, under active mining claims, or unsafe to enter — and often all three.
A record's presence tells you which rocks a county carries. It does not tell you that you may go there, and most of the time you may not. Sending readers to historic mine sites would be bad advice and worse citizenship; we don't do it, at any page depth.
Layer two: the legal-access directory
The places this site actually sends you — 159 at last count — are hand-compiled from official sources only: fee-dig operators' own pages, BLM and Forest Service designated-area pages, and state geological survey publications. Every entry carries the source it was checked against and the date we checked it.
Hours, fees, and access rules change. Verify with the operator or land agency before you go. That line renders next to every entry because it is true of every entry.
Listings are editorial, never paid. No operator can buy a place in the directory or a better description; that neutrality is the point of the site.
The standing rule
Before any trip: check land ownership and current mining claims, get permission, respect closures, and never enter old mine workings. It appears in the footer of every page because there is no page it doesn't apply to.
Reference data
The Mineral Quick-ID tool uses hardness, streak, and luster values from standard mineralogy references (the conventions of Klein & Hurlbut's Manual of Mineralogy and Mindat), simplified into field-test buckets a collector can actually perform with a fingernail, a penny, a knife, and a streak plate.