118 posts in this topic

Good information. Google earth is valuable for so many things. I use it to locate roads that are not mapped on USGS topo maps, I use it to see outcrops, and old time hand stacked rocks made by miners slucing gravels.

manVSgold likes this

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This is handy for graphic presentation of rock sample data i.e. pan sample results over a mining claim.

 

For geophysical applications, there are several possibilities.

 

- Geowizard

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Quote from Geowizard


 


There is buried treasure all over Alaska. The State has spent money to do the work. So, if money isn't the issue, then what's keeping so many other prospectors from using this free information? The Alaska Department of Natural Resources has spent and continues to spend Millions of dollars. The information is published online.


 Geowizard


 


Prospecting targets are not that hard to find but then it takes money and effort to advance a prospect into something of value. Please read “Rule of Thumb” # 101 (below) for another perspective of what it takes to make a mine.


 


Hard Rock Miner's Handbook Rules of Thumb


Edition 3 - 2003


Chapter 1 - Exploration Geology and Ore Reserves


 


Rule of Thumb


1.01


Discovery


It takes 25,000 claims staked to find 500 worth diamond drilling to find one mine. Source: Lorne Ames


1.02


Discovery


On average, the time between discovery and actual start of construction of a base metal mine is 10 years; it is less for a precious metal mine. Source: J.P. Albers


1.03


Discovery


On average, the time between discovery and actual start of production of a mine in an established mining district (“brown field”) is seven years. Source: Sylvain Paradis


1.04


Discovery


On average, the time between discovery and actual start of production of a mine in a district where there is no previously established mining activity (“green field”) is ten years. Source: Sylvain Paradis


1.05


Costs


The amount expended on diamond drilling and exploration development for the purposes of measuring a mineral resource should approximately equal 2% of the gross value of the metals in the deposit. Source: Joe Gerden


1.06


Bulk Sample


The minimum size of a bulk sample, when required for a proposed major open pit mine is in the order of 50,000 tons (with a pilot mill on site). For a proposed underground mine, it is typically only 5,000 tons. Source: Jack de la Vergne


1.07


Ore Reserve Estimate


The value reported for the specific gravity (SG) of an ore sample on a metallurgical test report is approximately 20% higher than the correct value to be employed in the resource tonnage calculation. Source: Jack de la Vergne


1.08


Ore Resource Estimate


To determine an “inferred” or “possible” resource, it is practice to assume that the ore will extend to a distance at least equal to half the strike length at the bottom of measured reserves. Another rule is that the largest horizontal cross section of an ore body is half way between its top and bottom. Source: H. E. McKinstry


1.09


Ore Resource Estimate


In the base metal mines of Peru and the Canadian Shield, often a zonal mineralogy is found indicating depth. At the top of the ore body sphalerite and galena predominate. Near mid-depth, chalcopyrite becomes significant and pyrite appears. At the bottom, pyrite, and magnetite displace the ore. Source: H. E. McKinstry


1.10


Ore Resource Estimate


Archean aged quartz veins are generally two times as long as their depth extent, but gold zones within these vein systems are 1/5 - 1/10 as long as their depth extent. Source: Gord Yule


1.11


Ore Resource Estimate


In gold mines, the amount of silver that accompanies the gold may be an indicator of depth. Shallow gold deposits usually have relatively high silver content while those that run deep have hardly any. Source: James B. Redpath


1.12


Ore Resource Estimate


As a rule of thumb, I use that 2P reserves are only such when drill spacing does not exceed five to seven smallest mining units (SMU). Open pit mining on 15m benches could have an SMU of 15m by 15m by 15m. Underground, an SMU would be say 3m by 3m by 3m (a drift round). Source: René Marion


1.13


Ore Resource Estimate


Your thumb pressed on a 200-scale map covers 100,000 tons of ore per bench (height assumed to be 50 feet). Source: Janet Flinn


1.14


Strike and Dip


The convention for establishing strike and dip is always the Right Hand Rule. With right hand palm up, open and extended, point the thumb in the down-dip direction and the fingertips provide the strike direction. Source: Mike Neumann


 


Rules of Thumb compiled by Jack de la Vergne and


McIntosh Engineering


 Page 1

Clay likes this

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Of course these rules of thumb are just that - general concepts that are good to remember.

Even with good geophysical targets, the odds are low that any particular one will develop into a viable, workable, profitable ore body.

 

Here is another "rule of thumb" - Geophysical testing data indicate 1000 of the next 10 valuable deposits to be discovered.

 

Geophysical testing is indeed something like a treasure map, but one with hundreds of worthless "X" points marked on the map in addition to one or a few valuable ones.

 

Determining which 10 of the 1000 indications are valuable commercial deposits and which are the vast majority that are artifacts of various geologic conditions that are not actually valuable deposits but are some other geologic condition, still requires drilling, geologic mapping, localized detailed geophysical surveys, soil sampling and other serious efforts from exploration geologists.

 

Drilling is still very hit and miss, and because it is terribly expensive, is reserved for only the best indications of a viable deposit where many indicators seem to show something in addition to geophysical data..

Developing a good deposit into a mine still takes huge amounts of money and effort.

Some types of mineral deposit targets do not show well in geophysical testing and still require geologic maps and a "boots on the ground" type of approach.

 

Gold and other products are valuable just because good deposits are hard to find.

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Here is another "rule of thumb" - Geophysical testing data indicate 1000 of the next 10 valuable deposits to be discovered.

 

:lol:  That's brilliant Chris, I'll be putting that into my bag of "what ifs" and rusty shovels!  :lol:

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Geo -

Seriously? I am not really sure what you are trying to say.

Are you saying that any target identified by you in regional scale geophysical testing is 100% likely to be a deposit that can be commercially mined at a profit? No need to drill or do any other tests?

You want an example of a deposit that does not show well on regional scale geophysical testing? How about the placer deposit you are mining at Ophir - there is one. There are many others.

By viable I mean a deposit that can be mined at a profit to the company and investors.

 

The process of going from interesting possibility to known and identified ore reserves is sort of like the number of bricks in the levels of a pyramid. At the bottom there are a huge number of interesting possibilities worthy of further investigation. Time and money are put in to review and test the raw "possibilities" and move them up the pyramid. Many methods can be employed for further defining the potential of the raw "possibilities", Some examples include soil sampling, local scale geologic mapping, local scale geophysical testing and others. Ones which still seem like good possibilities after the initial examinations and testing may get drilled. Some of the prospects which still are interesting after initial drilling may get more drilling. Those which still give good results will get closely spaced drilling to identify actual ore reserves in the ground. Finally, like the number of bricks near the top of the pyramid, there are only a few that end up as identified, quantified, ore reserves that can be mined at a profit. It takes a lot of time and money to move a raw possibility up through all the steps of exploration to the final stage of known ore reserves.

 

Geo, you yourself said in the original post which started this thread. that the regional geophysical measurements such as those by the state of Alaska could yield "possibly thousands of probable locations" - which is true. However, decades of experience in testing out and proving up the possible targets identified by these sorts of regional scale geophysical testing shows that only a small portion of the thousands identified will in the end turn out to be valuable deposits that can be mined at a profit. Will the number be 10 of each 1000? Who knows. The final number might be 30 of 1000 or it might be 5 of 1000. Only testing can determine which of your thousands might turn out to be real treasure, and which of the prospects for one reason or another are of no particular value - the worthless X points on the treasure map. However, many years of exploration experience demonstrates it will not be 999 of 1000, or even 500 of 1000 - it will be only a small percentage of the original number of targets.

Tad R likes this

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Geo -

I am not really sure what you are objecting to in my comments - you seem to agree with me on most things.

 

geophysical data provides a pointer to the location of conductive mineralization.

Of course - I've been saying that. Geophysical data is an important tool that is very commonly used by exploration geologists. Geologists use geophysical testing both on a regional scale (like the data you are looking at from the Alaska DGGS), as well as more local scales that examine claim blocks or other smaller areas.

 

Geophysical data provides a clue to geology and mineralization with structure that is not visible to geologists.

Exactly - that's why this type of testing is such an important tool for geologists. Together with other data, geologists use geophysical information to help them decide what areas are worthy of the expense of drilling. We are also in agreement here.

 

 

Maybe you should explain that to the scientists at Alaska DNR, DGGS (mostly senior, geology - PhD types).

So there is something here that you think I am wrong about which the geoscientists could set me straight on - and I am not really sure what "that" is. So let me know - maybe its just a misunderstanding between us. Just as a coincidence, a large number of the Alaska DGGS staff will be here in town in a couple weeks, so yes, I very easily could have a discussion with them in the near future.

The only thing that we seem to be disagreeing on is the fact that only a very small proportion of the raw potential deposit "targets" identified by geologists and prospectors actually end up becoming profitable hard rock mines. This includes raw targets identified by regional geophysical data such as you are seeing from DGGS. Is that what this is about? Is that what DGGS is supposed to tell me I am wrong about?  Let me know.

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