Somebody else should check my thoughts on this, since I am not as deeply well versed in lode claims...Bottom line up front: Surface exposed veins are part of your claim, this is different from a surface rights issue (and you would be more worried about claim access, in the case somebody did have surface rights to the land). Alluvial or colluvial deposits (eroded deposits as you described) would require a separate placer claim to protect (and you'd want it separate, because the eroded materials are not likely going to be a large part of the main vein in location anyway.)
As I understand it you'll want to claim what you expect has the greater yield and most closely matches the site details. Most sites are either lode or placer, but not both. (Imagine the exception: A river or glacier depositing gold in significant enough quantity to make worth chasing, all around a pre-existing gold vein or lode. Things like this can happen, but are pretty darn rare. The Golden Unicorn. If you did find such, then I would file both types of claims even if they overlap in a portion or heck even if they overlapped completely.)
It seems you have nailed down what you believe is the lode, so I would start there. (Common misconception is that the lode is most likely to be the highest yield for the lowest investment. Uh... sure, if you know the lode is bearing a geologically estimated value. Barring that, there could be as much or more gold waiting in the placers you suspect. But generally go with what you know first.)
If you do in fact have a vein of interest, claim that as a lode claim. Do as much research as you feasibly can to make sure your drawn parallelogram is likely to incorporate the lode to the best extent you can (since lode claims have very specific limits to size) and being as specific as to the type of material you are finding the valuables locked up in as you can. Loose materials from the veins/lode of that claim are generally protected when originating and maintained within the bounds of the claim, unless it can be proven as a result of natural processes (and thus be placer). Anything you store on the surface after banging it out of the lode is protected as yours, because none of that material is placer and it remains in your claim. Now if a juicy nugget was missed in your tailings (also yours, and as such your responsibility to manage to BLM's standards), and somehow was
naturally (or better stated, not removed by a claim jumper) washed down and off your claim, you'd never know and your gold just became
PLACER the moment it crossed that line. If that gold washed onto another person's placer claim... you couldn't pick it up without their permission. And the placer world thanks you for making their grounds a bit richer in the process, because you will likely lose
some (dependent on your recovery rate/processing methods).
If you have found resulting placers that originated from that vein (IE you are following the trail of float materials from the lode on down), then you want to target/test pan where you think the best resulting placers would be and file separate placer claim(s). (And I would be much more careful about picking those spots to file as a placer, going after the most likely spots and panning/sampling rather than guessing. You are going after far more than just what eroded out of your intended lode claim recently as you work it... I'd be asking myself "what has been deposited 100, 1000, 100,000 etc years back and where from my vein in the best 20 acres?") You can expand your area of interest if you can get co-locators to file with you as well, so that 20 acres covered can grow to 160 acres covered via association... not too tough to find people willing to do if you are coming up with reasonable placers from a source you have already identified. (A spouse, family, close friends, and kids 18+ are awful helpful to have in this case, too, because every one of them can act as a locator themselves up to the limit of 8 total in the association.) (And you never know, that spot might very well be in the eroded alluvium materials just hanging out right below your lode.)
Technically somebody can come to your lode claim and have a blast with anything that is from a collocated placer deposit, if that situation truly exists. For instance, somebody could file a placer claim simply designed to work on anything that floats out of your claim, but usually this is far less effective than going after gold that already existed as a placer prior to you just working the ground (we work with the presumption that you recover your gold decently from the lode, and not enough is going out to make it worth while on an annual basis). They could even feasibly file a placer claim on top of your lode claim, but they couldn't touch anything coming out of the veins/lode in your claim. (Just as you would no longer be allowed to process placers within their collocated claim.) But lode claims are typically very specific, narrow, and don't provide
any opportunity to protect surrounding placers at all.
Here is the BLM verbiage that you are probably interested in that explains which is which:
QUOTE
Lode Claims:
Deposits subject to lode claims include, classic veins or lodes having well defined boundaries. They also include other rock in place bearing valuable minerals and may be broad zones of mineralized rock. Examples include quartz or other veins bearing gold or other metallic minerals and large volume but low grade disseminated metallic deposits. Lode claims are usually described as parallelograms with the longer side lines parallel to the vein or lode. Descriptions are by metes and bounds surveys (giving length and direction of each boundary line). Federal statute limits their size to a maximum of 1,500 feet in length along the vein or lode. Their width is a maximum of 600 feet, 300 feet on either side of the centerline of the vein or lode. The end lines of the lode claim must be parallel to qualify for underground extralateral rights. Extra lateral rights involve the rights to minerals that extend at depth beyond the vertical boundaries of the claim.
Placer Claims:
Mineral deposits subject to placer claims include all those deposits not subject to lode claims. Originally, these included only deposits of unconsolidated materials, such as sand and gravel, containing free gold or other minerals. By Congressional acts and judicial interpretations, many nonmetallic bedded or layered deposits, such as gypsum and high calcium limestone, are also considered placer deposits.
Placer claims, where practicable, are located by legal subdivision (for example: Township 10 South, Range 11 East, Section 9, SE1/4). The maximum size of a placer claim is 20 acres per locator. An association of two locators may locate 40 acres, and three may locate 60 acres, etc. The maximum area of an association placer claim is 160 acres for eight or more persons.
The maximum size of a placer claim for corporations is 20 acres per claim. Corporations may not locate association placer claims unless they are in association with other private individuals or other corporations as co-locators.