Buying a placer claim comes with plenty of risks and you need as much information as possible about the mineral deposit in order to minimize those risks.
First and foremost, you need to visit the proposed site. To base a high level of credence (and expectation) on “what used to be” some 20 odd years or more ago, could prove more disappointing than not. What “used to be” remains a far cry from what may be, today.
Mineral reports, as well as the property itself, should be evaluated before buying or acquiring an interest in a placer property or mining operation. The only real way to evaluate a placer property properly is to walk as much of it as possible and see for yourself.
The evaluation should begin with the mineral report itself, if there is one, and can you make a profit by mining it. Check the average grade of the ground. How a mineral report answers this second question will make or break the property. This is of the utmost importance to the buyers and the sellers, so beware of deceptive wording. If there is misleading wording anywhere, it will be in the sample data and in reserve/resource estimates.
The potential buyer should try to figure out the mining and prospecting history. How many previous tenure holders, how much has been mined and how much is left to mine? Are there still values left in the ground and what is the tenor of the virgin ground? You want to see a lot of samples that were properly taken and accurately represent the material to be mined. There may be only a few random pan samples taken from a gravel bar or shallow pits, which are not indicative of the true values.
If the property has a history of production, then there should be adequate sample data and assay reports. So the amount and quality of sample data can depend on the degree of development of the property and can also reflect the professionalism or lack of it on the part of the previous owner.
You need to know what type of placer deposit it is. A stream or river placer can be a debris flow or a typical stream. The difference it makes is debris flows are dirtier and have the gold particles scattered throughout, while a typical stream placer is more likely to have a bedrock concentration as well as scattered gold and less mud.
Check for hand-stacked rocks and old mining equipment. Check for open shafts and prospect pits. Check to see if bedrock is exposed in the bottom of the valley, or old ditch lines on the hillsides. Perhaps some unnatural looking deposits scattered about the landscape. If miners were present, they may or may not have lived in a cabin and had campfires. Look for evidence of human activities, new or old.
Take notes on the thickness of overburden, the thickness of gravel layers, the depth to the water table, the depth to bedrock, and what the bedrock is doing. Make sure there is enough water for mining. Check for large boulders and clay, which may pose problems.
Check to see how much of the ground has been mined and how was it mined. Older mining done before the days of hydraulic excavators is to our benefit because they could not rip bedrock as effectively. Dragline miners used only the weight of the bucket and pulling for ripping bedrock. They could not increase the weight of the bucket by downward pressure as hydraulic excavators can now do. If bedrock was soft, then draglines may have done a good job of cleaning bedrock. Otherwise, they left gold on the bedrock.
Check to see if there are other mining properties close by. Check to see if they are placer or mineral tenures. Look into their mining activities and if the nearby benches been worked. A lot of this information can be obtained through Aris reports and the Mineral Titles Online.
In British Columbia, it is also very important to check as to whether or not the claim encompasses a Native Reserve. Many claims in the province overlap Native Reserves and the workable ground on many of these claims is very limited. It will also limit you to the area you can claim on your work reports, and you may not be able to extend your claim.
Sampling as much as you can while in the field is a given. At a minimum, pan sample every place that is convenient and where the claimant/miner recommends to sample. When sampling such sites, scrape off a few inches of the surface in order to minimize the risk of salting, and sample adjacent areas to those recommended by the owner. If the claim owner refuses to give you access, or sample the claim, then do not buy it! Reputable sellers will usually not have a problem with you testing the claim.
Shoot lots of pictures of everything relevant to the mining of the claim. Include landscape shots too because you may need all these refreshers when making your decision later on when you are back home or at your office and when other people are helping with your decision making.
Finally, take notes about the access to the property. Look for timber that must be dealt with, electric lines nearby, the elevation and climate, fish in the creek or other critters such as cougars and bears that may cause problems.
Many claims today are purchased online from the MTO (Mineral Titles Online). You can still do your research ahead of time. Check the claim history. How long did the previous owner have the claim? How many previous owners were there? Check the work reports. If the previous claim owners only had the claim for one year and let it lapse, then that would indicate one of several things. Either there was insufficient gold, they were a part-time enthusiast, or a claim flipper who was unsuccessful in mining the miner. It is important to find out which is the case.