A cache of locally-mined gold bullion so large that only a fraction could be transported on the first trip away from the mines. Five or more millions dollars reported, in old prices.
In the late 1700’s, a party of Frenchmen ventured deep into the Colorado wilds long before any roads had penetrated the area, and managed to find a rich Gold zone to mine. The large party successfully extracted a great deal of Gold, but started to suffer serious attrition as disease, lack of resources, accidents, and conflicts with increasingly hostile Native peoples took their toll. With diminished numbers, the few remaining prospectors cached the bulk of their Gold, supposedly in three main spots marked by well-made signs. After securing their riches, they started the arduous and risky trek to French-controlled territory with the added jeopardy of having to avoid the Spanish authorities. Even more tragedy befell the remaining adventurers and a man named Ledeoux is one of only two indicated to have survived. Several expeditions are said to have sought the caches, using a map passed down through the generations as a guide, but none are reported to have yet succeeded, including more modern efforts. A false grave, shadow signs, and symbology incorporating the fleur de lis are all mentioned, but the best that any search is reported to have found is an old hidden shaft that turned out to be empty.
Dates and numbers of members in the original, pre-departure, and final parties from several different references are:
Western Treasures Lost and Found: 1790, two made it back.
Lost Mines and Buried Treasures: 1790, 300 men, less than 15 started the return, two made it back.
Southwestern Ghost Town Atlas: 1780.
Colorado’s Lost Gold Mines and Buried Treasure: 1790, 300 men, 17 started the trip back, two made it back.
Lost Mines and Treasures of the Southwest: 1770’s, 300 men, only Ledoux made it back.
A large mining effort that produced 5+ million in Gold (old value) would leave significant signs, and such a rich strike as reported would have real geological indications that can be identified. Any old artifacts should verify the presence of an old camp, and all old mines had the camp near them due to the difficulty of transportation in pre-1900 workings. Camps are usually downhill from workings. Also, since the story indicated refinement of the Gold, arrastres and smelter slag are other good indicators. As to the cache spots themselves, destroyed markings (as indicated in some stories) actually leave a trace all their own if the destruction involves large rocks or outcrops. Since the Frenchmen were likely hiding their operations in the then-Spanish controlled territory, trail markings and other signs would be kept to a minimum, natural features would be preferred landmarks, and camps and workings would be situated in locations out of sight from surrounding terrain.