A lode claim covers a vein or hardrock mineral deposit — gold locked in quartz or rock. A placer claim covers loose, alluvial deposits — gold settled in stream gravels, benches, or ancient channels. The type of claim you file must match the type of deposit you've found; using the wrong type can make your claim legally defective.
A lode claim covers a vein or hardrock mineral deposit — gold locked in quartz or rock. A placer claim covers loose, alluvial deposits — gold settled in stream gravels, benches, or ancient channels. The type of claim you file must match the type of deposit you've found; using the wrong type can make your claim legally defective. The question comes up at every mining camp: lode or placer? Pick the wrong one and you could spend months working ground you have no legal right to mine. Pick the right one and the 1872 Act protects your location as long as you keep paying the annual fee. Here's how to think about the distinction in practical terms — and when it gets complicated. A lode claim is designed for mineral deposits that are in place — meaning still in the original rock formation they formed in. Classic lode targets include gold-bearing quartz veins, copper porphyry systems, silver-bearing sulfide deposits, and epithermal gold systems. The 1872 Act allows a lode claim to extend 1,500 feet along the course of the vein and 300 feet on each side of the vein centerline, for a maximum of roughly 20 acres. Two people can locate a single lode claim as co-locators, but each person can only locate one additional lode claim on the same vein within the same 1,500-foot segment. The legal requirement for a valid lode location is that you have actually discovered a vein or lode of quartz or other rock carrying valuable mineral. A real discovery — not just color in the soil — is required to make the location defensible. If the gold has been physically moved from its original source rock by water, erosion, or gravity and deposited in a different location, it's placer gold. Stream gravels are the most obvious example — but ancient bench gravels high above the current stream, residual deposits at the base of a weathered vein, and eolian (wind-deposited) sands also qualify as placer deposits. The size limits for placer claims are different. A single locator can claim up to 20 acres. Two people can claim 40 acres together. Eight or more people can combine to locate an association placer of up to 160 acres — a full PLSS section — in a single location act. This is the mechanism behind many of the large 160-acre claim blocks you see on MLRS maps. The rule of thumb: if you found it by panning a stream, it's placer. If you found it by chipping at rock outcrops, it's lode. But a lot of real-world prospecting lands in a gray zone. Courts have long held that if you locate a lode claim on ground that actually contains only placer deposits (or vice versa), the location is void. When in doubt, file both a lode and a placer on the same ground — the law allows this, and it costs only the additional filing fees to cover your bases. A mill site claim covers non-mineral land used for processing, milling, or other support operations for a mining operation. Maximum size is 5 acres. The land must be non-mineral (no valuable deposit) and must be used or occupied for mining or milling purposes. Mill sites are separate locations from the mining claim — they protect your camp, processing area, or access route from competing locators. The least used type, a tunnel site claim allows a prospector to drive a tunnel into a hillside to prospect for lode deposits. The tunnel gives the locator rights to any lode veins cut by the tunnel as it advances, with a possessory right to 3,000 linear feet of tunnel direction and 1,500 feet on either side. Once a vein is cut, a separate lode location is required to hold those rights. You're looking at a BLM mining claim record and you see something like "T14N R8E S22." What does that mean? Or the claim lists its PLSS_DESC as "N2NWNE" — and you're supposed to figure out exactly where on a 640-acre section that claim sits. The PLSS was designed in the 1780s to survey and divide the frontier land of the new United States into orderly, saleable parcels. It's been in use for over 240 years and underpins virtually every federal land record in the west. Once you understand the logic, reading a PLSS description becomes second nature. The PLSS covers 30 states — primarily the west, midwest, and Great Lakes region. It does NOT cover the original 13 colonies, Texas (which retained its own lands after joining the union), Hawaii, or most of the original territories governed by Spanish/French land grants. For prospectors this matters: if you're working in Virginia, Georgia, Tennessee, or Texas, you won't find PLSS descriptions on state land records because those states use metes-and-bounds surveys instead. BLM claims only exist on federal public domain land, which is primarily in the 11 western states. The PLSS starts with a principal meridian — a north-south reference line — and a baseline — an east-west reference line. The continental US has 37 principal meridians. In Nevada and California, surveys are referenced from the Mount Diablo Meridian. In Arizona, the Gila and Salt River Meridian. In Wyoming and Colorado, the Sixth Principal Meridian. From the principal meridian, the land is divided into townships: 6-mile-square blocks arranged in a grid. A township's address is its position relative to the baseline (north or south) and its range relative to the principal meridian (east or west). "Township 14 North, Range 8 East" (T14N R8E) means the block that sits 14 townships north of the baseline and 8 ranges east of the principal meridian. Each township is divided into 36 sections, each covering one square mile (640 acres). Sections are numbered starting at the northeast corner of the township, running west to east across the first row, then doubling back east to west across the second row, and so on — a boustrophedon pattern (ancient Greek for "as the ox plows"). Section 1 is always in the northeast corner. Section 6 in the northwest. Section 36 in the southeast. "T14N R8E S22" means Section 22 of Township 14 North, Range 8 East — a specific 640-acre block you can find on any PLSS map. A section is divided into four quarter sections of 160 acres each, named by their compass direction: NE¼, NW¼, SW¼, SE¼. Each quarter section covers 160 acres — a standard 20-acre association placer claim covers an eighth of a quarter section. You can subdivide further: the NW¼ of the NE¼ is a quarter-quarter section of 40 acres. The N½ of the NW¼ of the NE¼ is 20 acres. This is the aliquot notation system — and it's exactly how BLM MLRS records describe the precise footprint of a mining claim. Every BLM mining claim in the MLRS system is described using PLSS notation. The legal land description on your Notice of Location must use PLSS to pinpoint your claim. The BLM uses PLSS to map claim boundaries and identify adjacent or overlapping locations. The PLSS_DESC field in MLRS — which you'll see if you query raw BLM data — contains the aliquot description of the claim's precise footprint within a section. AuthoriProspector parses this field to shade the exact 20-acre aliquot that's claimed, rather than coloring the entire 160-acre section block. Here's a real-world scenario: you look at a BLM claim block on a map. It covers what appears to be a full 160-acre quarter section — a solid red rectangle on the screen. But you know that placer claims are limited to 20 acres. So either the map is wrong, or there are multiple claims stacked on the same 160-acre block, each covering a different 20-acre piece. The PLSS_DESC field in BLM's MLRS is the key to understanding exactly which 20-acre slice each claim covers. If you can read aliquot notation, you can look at a cluster of claims and immediately know how much is actually open. Think of a 640-acre section as a square. Divide it into quarters (N, S, E, W directions give you NE, NW, SE, SW). Each quarter is 160 acres. Now divide each quarter into quarters again — you get 16 cells of 40 acres each. Cut each 40-acre cell in half (north or south half), and you have 32 cells of 20 acres each. Those 20-acre cells are the standard aliquot used for individual placer claim locations. The PLSS notation for each cell builds from the smallest subdivision outward. Reading the notation right-to-left takes you from the largest subdivision to the smallest piece. When BLM renders claim polygons on a map at the section level (160 acres), it often draws the full quarter-section rectangle even when the PLSS_DESC says the claim is only 20 acres. The map is drawing the bounding box of the legal description, not the precise aliquot footprint. This is why you can see a solid-red 160-acre block on a BLM map and still find open 20-acre parcels inside it. The block represents a section with some claimed cells — but the unclaimed cells are still available for location. You have to parse the PLSS_DESC of each claim in the block to figure out which cells are taken and which are open. You find a claim record with PLSS_DESC = "N2NWNE" in Section 14, Township 7 North, Range 3 East. Reading right-to-left: start at the whole section, take the NE quarter (160 acres), subdivide that into the NW quarter (40 acres), then take the north half (20 acres). You've arrived at a 20-acre parcel in the northern interior of the section's northeast corner. The south half of the same 40-acre cell — "S2NWNE" — is a separate 20-acre parcel that could be open for location. So could the NE of the NW ("NENW"), the NW of the NW ("NWNW"), and the other 28 aliquot cells in the section. When you drop a GPS stake pin in AuthoriProspector, the app reads the PLSS parcel data for that coordinate and returns the aliquot notation — down to the 20-acre cell. The Auto-Square feature then uses that notation to pre-populate the legal land description field in your Notice of Location PDF. No need to manually compute which aliquot your pin falls in.
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