Gold VDI Responses: Testing a Cross-Section of Rings
Much of the reason that this book has such an emphasis on basic skills is because gold cannot be recognized by any single characteristic or feature. My hope for readers is that they will develop the ability to combine: a savvy understanding of sites; with the basics of identifying good targets, and the DFXs excellent array of target information to become more accurate and effective treasure hunters. Going out and finding gold is the acid test for all these skills. Understanding gold VDI responses is a big part of developing this accuracy. Its worth mentioning here that a lot of jewelry items now have what can be called fancy finishes. These finishes: distressed, knurled, battered, brushed, gloss, for example, often require different formulations for the gold that will be used. This skews bench testing to a certain extent in that a small item may read higher than a larger one because silver or copper is used in larger amounts in the formulation.
With identifying gold in the field, there are always exceptions to any rule--but overall, there were some interesting patterns that emerged in the test. The rings chosen for this test were picked on the basis of graduated size--I looked for items in each size range and karat designation. With some I had to go with what I had. Its worth noting how objects of similar karat and weight can have completely different VDI values. All tests were bench--that is, in air.
The values are shown in the same way as the DFX cycles-- through several digits. When I say cycles this is based upon the observation that as noted in the text, generally you will see two numbers that are close together (as the objects composition and shape permit) and then one that is further out. After this the reading will centralize again and repeat the sequence. This is not always the case in that many targets display this pattern in reverse--gradually centralizing although this could reflect shape or coil movement. Not all test items went to a third digit--reflecting likely the shape and narrow alloy formulation.
1/ 22 Karat (.916)
1/ 9.3 gr. = 48, 49
2/ 10.0 gr. = 51, 48, 49
3/ 12 gr. = 63, 64, 61
4/ 7.5 gr. = 39, 41
These were all mens rings, smaller sizes. 22 karat gold usually has silver added for hardness--bringing up the reading and often making for a wider response range. Copper is used similarly to give it a more orange appearance. These pieces had the narrow VDI of clean, high karat gold--something to watch for among screw-cap-range responses. Its worth noting as well that not much else falls into this VDI area. If you know a site where a lot of East Indian picnics or festivals take place, this is what to look for.
2/ 18 Karat (.750)
1/ 11.6 gr. = 48, 46, 52
2/ 10.8 gr. = 55, 54
3/ 10.8 gr. = 57, 57, 58
4/ 7.5 gr. = 38, 39, 41
5/ 2.4 gr. = 18, 17, 21
Of those rings of substantial size many of these fell into a predictable range as well--certainly good news! As mentioned in the section on Running Notch Programs +38 or +39seemed to be the bottom of the range for those items tested. 18 karat is also a clean signal--especially when it is in the form of a band or rounded ring. Its the mens rings (signets etc.) that have the outsized crown which tend to give a wider pattern--often because they are upended or you are hitting them end-to-end and back. A lot of 18 karat gold also has silver or copper added for color, sheen or hardness too, so these tend to be high-responding targets. This is especially true of white gold, which contains silver as a large part of its alloying. Its also why you rarely see any 18 karat responding in the typical low-gold spot of +/14 / +16 where so much 10 karat comes in.
3/ 14 Karat (.585)
1/ 12.0 gr. = 32, 31
2/ 11.0 gr. = 44, 45
3/ 8.1 gr. = 29, 27, 23
4/ 7.0 gr. = 48, 45, 46
With 14 K, the responses get a bit wider as you have almost half the object being made of other metals. Something a bit more typical than these might be closer to +39 or, +41. Based upon some of the 14 karat rings I have found with the DFX these are all quite good examples, especially those in the mid and high 40s and less commonly, those around +30. This grouping also has a good example of a disparity between size and VDI with items 1 and 4.
4/ 10 Karat (.410)
1/ 9.8 gr. = 17, 15
2/ 7.4 gr. = 23, 21
3/ 6.7 gr. = 35, 32
4/ 5.3 gr. = 45, 44, 47
5/ 5.3 gr. = 38, 39, 36
6/ 5.0 gr. = 25
7/ 2.0 gr. = 14, 12
As with the 14 karat, this group does not predict well by weight. They are still consistent, tight signals though--certainly more so than most tabs.
With the small pieces like number 7 accuracy is all about coil control. Where a consistent, even sweep produces the same gold range VDI numbers--dig. Where you see the response dropping way down into the foil zone, --dont get your hopes up. These responses are also less restricted to any given ranges. At most sites, the majority of lost gold will be 10 karat, so being objective and alert for the narrower VDI patterns is what will help you find more of these. My hunting partners and I are always joking about who is the sister ring or flyspeck specialist, but with gold prices on the rise, these bits certainly add up. The +14 to +27 range is where a lot of 10 karat items come in so be sure to thoroughly examine any solid indications of this type. More generally, look for small narrow indications that carry well over distance. By carry I mean a response that keeps its strength over distance. Foil does not do this and with practice its possible to be alert to the difference between these weak responses and the sharp, high-conduction of gold. A signal showing +14, +16 is very good--dig that one for sure! 9 karat (.333 to .375) is another kind of low-karat gold that often turns up. This is often quite a high-responding signal in that there is a lot of room for other metals in it with copper, nickel and brass being among those used most often.
A general primer on where gold shows up on the DFXs VDI scale would be to look for narrow responses in the teens, 20s, low thirties, and above 38--going up to about 60 or more for extreme lunkers. You could also divide these into two VDI sections. With the lower two, there is much more junk that will mimic gold. When you get up over +38 you are dealing with larger objects, that will be more identifiable in terms of shape. Anything that is round is either something unusual or one of the larger tab varieties--not all that common. Ground cover is also a factor with this size of signal.
From: "DFX: From Beginner to Advanced"
by Clive James Clynick (clivesgoldpage.com)
