Hey Hobbyist --
Glad you are the happy owner of a new Gold Bug Pro!
As for a "list of target ID numbers of naturally-occurring metals," such a thing really doesn't exist. Unfortunately, metal detectors do not actually "sample" the TYPE of metal you are dealing with. While I don't know in depth how the "ID" processes work on the machine, I do know that the size of the target matters, and the "conductivity" of the metal matters. Basically, different types, different sizes, and different orientations of various metal targets affect the electromagnetic signal which is transmitted from the detector in different ways. And it is these "effects" on the transmitted signal (when that signal is re-acquired by the receive coil), that the machine "reads" and processes -- and tries to identify. But, like I mentioned, different sizes and different types of metals result in different IDs. For instance, a very small piece of shredded aluminum can will often read in the 40s on your Gold Bug Pro (similar, by the way, to where a very small piece of gold jewelry may sometimes read). However, a round aluminum screw cap, smashed flat, will often read in the low 80s -- like a penny or dime. Both targets are aluminum, but the round "coin-sized" aluminum cap reads more "coin like" than a small, jagged piece of shredded aluminum. Likewise, a small, 90% silver dime might read 84, whereas a larger 90% silver half dollar might read 90. My point is, the shape, the size, and the type of metal matters to the machine in terms of ID; the orientation of the metal also matters (a coin "on edge" will read differently than a coin lying flat), and finally, multiple targets in close proximity will also affect the ID (i.e., a large nail on top of a small coin will alter the ID of the "target," since the "target" in this case is actually two pieces of dissimilar metals). This is why folks will tell you that you should not rely completely on the digital ID ability of the machine alone, when making a "dig vs. no dig" decision. The Gold Bug Pro, in my opinion, does a very good job with its ID ability, but no machine is perfect, or even close to perfect. One approach to hunting is, certainly, to dig only the repeatable, solid IDing targets, but doing so, you must understand that a.) you will miss many good targets that way, and b.) you will STILL dig some junk (like the smashed aluminum screw cap I mentioned, for instance, which reads alot like a coin).
One more thing...you metioned a "10 inch wide patch" that gave a high VDI number. I have good news and bad news...the bad news is, that is likely a large piece of either rusty iron, or a flattened aluminum can, something like that. The good news is, though, that you were able to discern that it is a large, non-coin-sized target. This is information that you can use to your advantage. The ability to "size" and "shape" a target is an important skill to learn as a detectorist, and it can help you, as it is an additional piece of information you can use in terms of trying to decide what is lying under your coil. You can use that "sizing" ability to your advantage. It is POSSIBLE that what you have found is a "coin spill," i.e. multiple coins in close proximity making the "target" appear to be a single large one, instead of multiple closely-located smaller ones, but -- a reading that high (low to mid 90s) is probably too high to be coins -- unless you have found a spill of silver dollars!
Anyway, bottom line, is you probably need to spend some time digging ALL targets, to get used to what the machine is telling you. And I don't mean just "telling you" with respect to the digital ID (VDI) number; I am also referring to other ways the machine "speaks" to you, such as the likely size, the depth, etc. of the target. You will learn all that by digging EVERYTHING, and then relating it to what the machine was "saying". With time, you can begin to "guess" what is under your coil, based on your experience. Then, later on, you'll get pretty good at it -- though, I promise you, the "surprises" will never end!
Good luck, and I hope I made the point that no hobby-type detector is actually able to "read" the "type" of metal under the coil. Gold, in particular, reads just like many common types of trash (pull tabs, small aluminum pieces, nickels, etc. etc.) Dig everything, or most everything, for awhile, until you learn the machine. It's a great machine, but deciphering what it may be trying to tell you will take some time (and expect to dig up a BUNCH of junk for awhile), but don't get discouraged. The better finds will begin to become more numerous with time.
By the way, I don't know about the speed of the processors, but this machine, as compared to many others, is FAST! The fast processors, and really good coil, allow you to see -- individually -- many closely-adjacent targets, whereas slower machines with different coils would often only see one large target. You got a very good machine, but take time to learn what it is telling you, and you'll start finding good stuff soon!
Take care,
Steve
P.S. -- I made a "guess" that you are a new detectorist; if not, then you probably already know much of what I said to you in this post, so please take no offense if I spoke "down" to you. My assumption that you are new to the hobby may have been totally incorrect! Just trying to help!
I've printed out your post and stapled it to a photocopy of the manual which accompanies me out to the field. It will be a very handy reference. I may be just a hobbyist, but I take the effort to learn each machine as best I can. And that means taking to heart your great info!
