Sandy1, not to detract from your method, but I seem to remember there a way to capture aura's or something like them with a Polaroid ?, maybe that was something different, I cant remember exactly and I've slept since then
Discussion of this method surfaced in the 1990s - came out in a private TH newsletter of those times, as I recall. An electronics whiz friend of mine in CA tested it with encouraging results by hiding raw gold then applying the method. He gave it a tentative thumbs up, which was impressive since he was skeptical of many gold-finding quack schemes and devices.
Here's how it works, allegedly. The searcher needs a Polaroid instant camera with
SX-70 film. It only works with SX-70 film, which has not been produced for years now. SX-70 presumably was produced with a unique silver compound that happened to be effective for this method. I believe there may be (or was) a third-party producer of a suitable substitute film pac, but I'm not sure. There may also be old oem SX-70 film pacs available somewhere too, but it would be pretty old and possibly degraded with time - again, I don't know. The idea is to take a picture of the suspected cache site just and only right at sunup with the sun forming a right angle with the photographer and the cache. When the picture develops, an aura appears where the cache is.
My friend's results were positive. He noted that the 90 degree angle was critical, although a slight variation of a few degrees was OK. The further away from 90 degrees, the fainter the aura on the picture. Beyond a few degrees, there was nothing showing. Depth of burial didn't seem to matter, although he didn't bury his test gold real deep. His verdict was that if a searcher thought he knew where a cache might be, the SX-70 method may be useful, but for more random searching, the odds of using exactly the correct setup were probably too low to be of any help.