Lodes are deposits of mineral in place, regardless of their origin. The mineral must be firmly contained or embraced in solid rock. This includes veins with distinct hanging and foot walls, replacement deposits in sedimentary formations, ancient stream channels now consolidated in sandstones, such as the uranium deposits of Wyoming, and disseminated deposits such as the copper porphyries of Arizona.
On the other hand, mechanical deposits of minerals such as gold contained in the gravels of stream beds and alluvium deposits are properly located as placer claims. However, certain rock types, such as marble and perlite while mineral in place, are properly located as placers since the Act of 1892 provided for locating building stone under the placer mining laws. Included are bedded minerals not contained in rock in place, such as bentonite.
The discovery requirements for a lode claim are that the mineral must be in place. A discovery of float (a loose piece of ore from a vein) is insufficient. Merely a trace of mineral is insufficient. Discovery by geologic inference is insufficient. There must be an actual and physical exposure of a lode.
The discovery must be on vacant public domain, which includes patented surface lands with minerals reserved to the United States.
There have been many court cases and decisions as to what constitutes the discovery of a valuable mineral deposit and it can be a difficult and complicated matter. The general rule is stated in the famous Castle v. Womble Decision, 19 L.D. 455, 1894: “When minerals have been found and the evidence is of such a character that a person of ordinary prudence would be justified in the further expenditure of his labor and means, with a reasonable prospect of success, in developing a valuable mine, the requirements of the statute have been met.”
In the Jefferson-Montana Copper Mines Co. case, 41 L.D. 320, 1902, it was stated that the following elements of discovery are necessary:
“1. There must be a vein or lode of quartz or other rock in place. 2. The quartz or other rock in place must carry gold or some other valuable mineral deposit. 3. The two preceding elements, when taken together, must be such as to warrant a prudent man in the expenditure of his time and money in the effort to develop a valuable mine.”
The extent of discovery will vary with the situation to be considered and the type of mineral and deposit. For example, the requirement as between two claimants is far less than that between a claimant and the United States. A mineral of intrinsic value such as gold may well be considered under the rules set forth above, but a more common mineral would be further subjected to a test of marketability.
In the course of patent proceedings, a mineral examiner of the Bureau of Land Management, the Forest Service if the claim is in a national forest or the National Park Service if the claim is in a national park or monument, will make a field investigation to determine the validity of the claims in question.
Each location must be shown to be more valuable for minerals than for any other purpose and the burden of proof rests with the claimant. The claimant must be prepared to show the actual physical discovery and substantiate the value through assays, drill logs, etc.