Mineralization?

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Mineralization?

Post  Kon61gold on Fri Nov 24, 2017 7:51 pm

G'day fellow prospectors

I wish to discuss ground mineralization, what is it, how it forms & the effect it has on metal detectors.
Firstly how can mineralization be defined?  Basically, mineralization can be defined as the amount or degree of iron/ferrite content present in the soil, or in a section or pocket of soil.  
The higher this iron buildup mixture in the soil/rock/clay layer is, the higher the degree of ground mineralization will be present & or vice versa.
How does mineralization form? Basically put, mineralization is formed through erosion of the surrounding host rock/s.
Now without getting to scientifically/geologically complicated, mineralization is formed from the decomposition/weathering process of the surrounding host rock, rich in iron/ferrite composition. (such that of decomposing ironstone rich loads or reefs near by).
Clay is formed by the decomposition or erosion of the surrounding host rock over time. When soil or clay is mixed to a certain degree of iron rich particles, it becomes mineralized.
The higher the iron absorption/mixture into the clay or soil, gives us the degree of mineralization, such that of what we know to be as, low, medium, high or in some cases extremely high mineralization.
The higher the degree of iron content mixed in with the soil, rock or clay layer, the greater the mineralization effects will be (in terms of ground noise) to a metal detector. Areas or ground of high or extremely high iron content, are considered areas of very high mineralization, & have a tendency of increased magnetic properties of the soil, as well as an increase in the electrical conductivity, making it difficult for metal detectors to quietly work over.
Not all ground noise is related to high iron content. Carbon in its crudest form "coal" (being a mineral not a metal) is not electrically conductive, but when  put through high temperature/pressure, (such that of a great intense bush fire) can over time, transform carbon/coal, into crystalline graphite, making it electrically conductive, as well as conductive to the coil of a metal detector.
Isolated pockets of clay domes, are mixtures of certain iron oxides, of such that mentioned above & when removed from the ground, spread out & broken up, tend to lose their mineralized strength, (similar to that of a highly mineralized pocket of soil) hence weakening their responding signal strength, to the metal detector/coil.

Cheers Kon.  T25
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Re: Mineralization?

Post  au-fever on Fri Nov 24, 2017 10:44 pm

Hi Kon

Further to that there can be more than one layer of mineralisation in the soil as well, as the ground surface is laid down over time with the weathering of host rock, rain washing, and wind blowing dust particles about and so on it can form many layers of soil from different periods in time, some layers can be benign and others that are highly mineralised, also you can have saturation of salts in areas that are not salt lakes that make the ground difficult as well.

The first layer of course is the surface, that's the fist thing we do when we hear a target is scratch the surface with a boot or pick, then as we dig down we remove other layers of mineralisation as well, later model detectors are better at handling the mineralisation than earlier model detectors, some earlier machines can achieve very good depths in benign ground as easily as the later detectors but they cant handle the mineralisation as well and that's why the later machines will get smaller nuggets much deeper than the early ones can as they cant punch through the layers and remain quiet enough so that you can distinguish the target response.

The various layers of mineralisation are the reason that nuggets can be missed as they can be sitting below a layer of mineralisation that is just at the limit of the detectors signal penetration, the pulse might hit the layer and spread out rather than pass through it and therefore not see the target and perhaps this spreading can happen on each layer in some very active areas really limiting the detectors depth ability, I have noticed also that in some places I always do much better with a small coil than a bigger one, maybe its because the more defined and compact pulses that it puts out will just simply penetrate the mineralised layers in ground more easily, all food for thought


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Re: Mineralization?

Post  deutran on Sat Nov 25, 2017 2:47 am

Thanks Kon and au-fever for some excellent info on this subject.As au-fever described often in high mineral ground the choice of large coils actually has a negative effect on depth or deep targets.Ive encountered this on many occasion.
I often think about it this way,maximum depth starts out in free air and anything in between thats conductive or magnetic required a degree of compensation or ground cancel/balance which results in some loss of depth.Sometimes the mineralisation is so high that the targets become lost even at shallow depths and this is why the new timings/technology specifically targets this type of ground.
We all know how much gold was found with the newer detectors working quietly in this type of ground that was invisible to the old detectors.
Unfortunately the mineralisation is not a constant factor requiring constant adjustments to the machine to maintain max depth at all times.This is often the main reason gold is missed especially during patch hunting or when working too quickly.
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Re: Mineralization?

Post  Kon61gold on Sat Nov 25, 2017 2:59 am

Yes, au-fever, all food for thought. There are other in ground variables or factors that affect or influence the degree of mineralization, some to numerous & long to go into, such that of temperature/moisture changes in the earth, which can all play a role towards increasing or decreasing the effects of ground mineralization on a detector, in way of ground noise.
This is why it is always better to prospect or swing a coil, over known mineralized ground, during the coolest part of day, (when ground mineralization is at its lowest or minimum noise level strength), making detectors easier to ground balance & more stable during operation.
Salt saturation levels within any given area are dependant on the temperature of water. The higher the temperature of water containing saturated salts, the greater the salt saturation % level will be, within any given section of ground. The higher the salt concentration, the greater the electrical conductivity of the ground will be, hence the greater the ground noise it will have on a detector, drowning out all hope of hearing the deeper fainter in ground targets.
So much more can be said about mineralization & its effects on detectors/coils & or in ground undisturbed buried targets over time, but I'll leave that for another day.
Thank you for your input Steve.
Mineralization is a subject that many a detectorist finds it difficult to get ones head around it (including myself). This is why discussing as many reasons as to how or why mineralization plays the role it does on or in ground, maybe can help all of us understand it better, in how to best tackle it, with any given coil/metal detector.

Cheers Kon.  T25
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Re: Mineralization?

Post  Minermike on Sat Nov 25, 2017 3:46 am

On the beach , coins tend to go with the black sand. The black sand is mineral but it knocks the depth down . You can get a layer of black sand under the clean sand . Black sand on the beach is a good place to go but expect a reduction of depth .
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Re: Mineralization?

Post  au-fever on Sun Nov 26, 2017 10:35 pm

This is an interesting read and covers the subject of mineralisation and its effects on a metal detector.

https://www.minelab.com/__files/f/11043/KBA_METAL_DETECTOR_BASICS_&_THEORY.pdf

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Re: Mineralization?

Post  Kon61gold on Mon Nov 27, 2017 2:15 pm

Good read indeed au-fever. Now all that remains, is to finding a way for detector technology, to better match, or keep up with the variably changing mineralized ground conditions, (from one meter to the next), whilst at the same time maintaining a clearer signal response, to a majority type/size gold, without the loss of depth, associated with the increase of mineralization. Shocked Q35 Technically speaking, it all sounds good on paper & under controlled lab conditions, until we put all that brilliant theory to prac, over a known mineralized gold field. Mind you, even though major metal detecting companies such that of Minelab, (who are leaders in the world of hand held metal detection technology) are constantly striving/progressing & succeeding towards bettering metal detecting technology, however, it remains quite obvious that, because of the many in ground mineral variable/gold nugget varieties involved, (one to many so called "windows" still remain) it will always be a slow, constant, tough (but progressive) challenging battle.

Cheers Kon. Q11
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