Overlap Analysis
Comparing the boundaries of mining claims with each other and with withdrawals and land status to find where they coincide, then checking the records to see which overlaps are real.
Detailed Definition
Overlap analysis compares the boundaries of mining claims with each other, and with withdrawals, private land, and other land status, to find where they coincide. It is a working method rather than a legal term. The map comparison finds candidates; the records decide which overlaps are real and what they mean.
Why map overlaps need checking
BLM's national mining claim data comes from MLRS. Its metadata states that "the BLM only requires that mining claims be identified down to the affected quarter section(s)," and that "claim boundaries, as staked and monumented, are found in the accepted Notice/Certificate of Location as part of the official case file." The map shapes are "primarily derived from Legal Land Descriptions (LLD) for the case and geocoded (mapped) using the Public Land Survey System." Two mining claims in the same quarter section will overlap on the map whether or not their staked boundaries touch.
The metadata also scores how well each case mapped. Some cases are "mapped to the Section," some "map to the County," and for some "no geometry is in the NLSDB, and only attributes exist." A case with no geometry will not appear in a map overlay at all.
Overlaps with other mining claims
A lode locator holds "the exclusive right of possession and enjoyment of all the surface included within the lines of their locations" (30 U.S.C. 26), so two mining claims cannot both hold the same ground. BLM's brochure "Mining Claims and Sites on Federal Lands" puts the burden on the locator: "it is the claimant's responsibility to determine if there are prior existing mining claims on the ground." Which mining claim prevails turns on dates of location and validity; see Seniority and Claim Conflict.
Overlaps with land status
Locating a mining claim "on lands withdrawn from mineral entry at the time you locate it" is a defect that cannot be cured and results in forfeiture (43 CFR 3833.91(c)). Master title plats, "a mapping of current land status for a specified township" (BLM Land Records), show patents, withdrawals, and other actions to compare against each mining claim's date of location.
Steps
- Pull every mining claim case in the area, closed as well as not closed, since BLM publishes the two sets separately
- Overlay them on the PLSS and on land status from master title plats
- For each apparent overlap, get the notice or certificate of location and map from the BLM case file and the county record
- Plot the staked boundaries from those documents
- Compare dates of location with each other and with withdrawal and patent dates
- Check each case's disposition and fee history
Why it matters in mining claim research
An overlap on a quarter-section map is a question, not an answer. Settling it takes the staked boundaries and the dates. Mining claim conflict analysis and reporting is built on this work. See also Controlling Ground and Claim Block.
Related Terms
GIS
A geographic information system: software and data that store, analyze, and display information tied to locations on the earth.
Seniority
The ranking of rival interests in the same ground, the earlier ahead of the later. Federal law ties some mining claim rights to dates, but BLM leaves disputes over possession to the courts.
Claim Block
A group of contiguous mining claims held by the same owner or group of owners, usually laid out to cover one mineral deposit and the ground needed to work it.
Controlling Ground
The ground a mining claim holder can actually hold once overlaps with other mining claims, closed land, and defects in the record are taken into account, as opposed to the acreage filed.
Claims Research
Finding and reading the records of the mining claims on a tract, from BLM and the county, to learn what is claimed, by whom, and whether the filings were made on time.
Claim Conflict
An overlap or competing interest between a mining claim and another mining claim or site, a patent, a lease, or a withdrawal on the same ground.
Spatial Join
A GIS operation that copies attributes from one layer to another based on where features sit relative to each other, not on a shared field.