There are two aspects to the historical investigation of the tale of the Lost Dutchman Mine.
(Note: The below is only a sketch of the history of the legend. Each topic is explored in depth in Part I, The Golden Dream and/or Part II, The Holmes Manuscript.)
1. The ability to prove the mine's existence through documentation is very unlikely. Waltz did not file a claim on this mine, although he did file claims on other mines. There are solid reasons why he could have found a rich mine in remote country and not filed a claim, and these are examined it Part I, The Golden Dream.
Since no claim was filed the only possible way to prove the mine through documentation would be if letters could be found written by Waltz attesting to the mine's existence. There are investigations going on on both sides of the Atlantic following these possibilities, but the chances of such letters, if they ever existed, surviving are not good.
Since the mine Waltz is reported to have found was originally a Spanish/Mexican Mine there could well be surviving records of these mines in official documents. According to some who have researched this possibility these records do exist, but they have not been made public. However, even if these records are found while they could prove that the Spanish did own and mine mines north of the Gila River there would be no way of proving that any of these specific mines were associated with Jacob Waltz.
First, there is Jacob Waltz. As stated we know that he was definitely an historical figure. From the historical record that he lived in Arizona from 1862 to 1891, that he was a miner and farmer, that he knew Peraltas, that he was caught in a flood and did know Julia Thomas and Rhinehart Petrasch.
From the accounts of people who knew Waltz we have stories of him leaving Phoenix with a pack animal in winter months and traveling east in the directions of the Superstition Mountains, we have accounts of people seeing him in the Superstition Mountains and we have accounts of him paying for merchandise with rich gold ore. The above certainly fits the legend.
According to the legend Joe Deering was a miner at the Silver King MIne who decided to search for the "Mine of the Two Soldiers" (see below) in the Superstition Mountains. As his supplies were running out he is reported to have found it, put up markers in a trail to the mine, then returned to the Silver King to work one month to get the necessary monies (capitol) to reopen a mine. At the Silver King he is reported to have taken on a partner, John Chunning. But, he did as the result of a sudden accident in the mine, and leaving Chunning with only partial information on the mine.
Joe Deering was an historical figure, he did work at the Silver King and he did die in sudden accident; the coroner's inquest on his death survives as do a newspaper article on the accident. Chunning existed and did hunt for a mine he said was based on information given him by Deering. At least three markers as described by Deering have been found in the mountains laying out a trial.
The Two Soldiers:
The legend says two discharged soldiers traversed the Superstition Mountains on foot, got lost and found an open mine with rich gold ore laying about. That they went to Pinal, inquired about work at the office of Aaron Mason, were told that the rocks they had were rich ore. They outfitted, left for the mine and were never seen again.
Pioneer reports tell of one of them being found shot in the back on the Marlow Ranch. There are pioneer accounts in newspapers of two men fitting their story in Pinal in the early 1880s. One researcher tracked down the names of the Two Soldiers, then their descendents. Further the descendents of Aaron Mason confirm the story, as do the descendants of Bob Bowen who worked in Pinal and was at the office of Aaron Mason when the Two Soldiers arrived.
Dick Holmes and Gideon Roberts:
The legend says that Dick Holmes and Gideon Roberts were at the deathbed of Waltz and that Holmes received a substantial amount of gold ore from the dying Waltz. Gideon is reported to have been about Waltz's age, suffering from "miner's lung" and to have died very shortly after Waltz.
Dick Holmes said he was at the deathbed of Waltz. Records show that shortly after Waltz's death Dick Holmes' life style improved -- he moved his family to new home with land and he bought a new horse and wagon. He did search for the mine for many years based on information he would only share with his son.
According to the records of the Robert's family and the Pioneer Cemetery Gideon Roberts did know Waltz, and he did die of "miner's lung" just a few months after Waltz died. Further, according to Gideon he was at Waltz's deathbed with Holmes.
Legend says the Peralta family were a prominent mining family in Sonora with mines also in what is now Arizona. The legend goes on to say that the family (including a Pedro Peralta) made an expedition to the mines in the 1840s, and that that expedition was attacked by a large group of Indians killing most of the party. This fight is supposed to have taken place on the western foothills of Superstition Mountain.
In 1928 Ward, the British counsel in Mexico, toured northern Mexico and reported meeting the prominent mining families, including the Peralta family. The patriarch of the family was a Blas Peralta, and there are records of his original land grant in Sonora.
I have talked with descendants of the Peralta family who confirm a family history of both mines in Arizona north of the Gila and an Amerindian fight in the 1840s. That fight was one that involved a large expedition to the mines north of the Gila. A Pedro Peralta was on that expedition (photograph of Pedro in Part I, The Golden Dream). This incident devastated the Peralta family.
Bob Crandall while working in Mexico City meant a Mr. Peralta and he (Peralta) also confirmed there had been a "massacre" of a mining party that went north, and that it placed a heavy burden on the family to this day.
Cowboys circa the 1890s working the vicinity where the massacre is supposed to have taken place reported finding quantities of human bones.
One of the more intriguing facets of the Lost Dutchman Mine legend is that the deeper one seems to dig into its history, the more one finds support of the basic story of Waltz having a mine, and having kept its location secret. If he buried and covered it the way he said he it may stay lost.