ancient and buried leads

[Barra_Mad]

Be to my brother in laws place which is built
On a reef, he has 3 old shafts there
And we hit one of the holes with a backhoe
No back breaking work and we
Found this..... Got the heart pumping
For a bithttps://www.prospectingaustralia.com/forum/img/member-images/3235/1408008032_image.jpg

Hey mate did you end up crushing some of that quartz. because the only way really to tell if a lode has gold in it is to crush it. I found similar looking stuff and its worth just on 1g per tonne but not rich enough for me to take to it with hammer and chisel. If you with in 50km of Ballarat you have the problem / curse of nuggety gold where its not in nice veins you can follow but is haphazardly distributed in the quartz lode.

 

[dwt]

As Ryan27 stated earlier these sections between the shafts are known as pillars, they have been left behind as ground support for the surrounding area, attempting to mine through these can be extremely hazardous, usually a team of highly expierenced engineers and miners are used to do this, the ground needs to be replaced as you are mining through it, pay particular attention to the ground before taking samples, there is a term we use in mining called "keystones" this basically means if you remove a rock the size of a tennis ball (when taking samples) you can bring down tonnes of dirt, not trying to discourage you mate, just letting you know of some of the dangers associated with hacking into remenant pillars, wether they be 10 feet down, or 1000 feet down.

 

[Ryan27]

As Ryan27 stated earlier these sections between the shafts are known as pillars, they have been left behind as ground support for the surrounding area, attempting to mine through these can be extremely hazardous, usually a team of highly expierenced engineers and miners are used to do this, the ground needs to be replaced as you are mining through it, pay particular attention to the ground before taking samples, there is a term we use in mining called "keystones" this basically means if you remove a rock the size of a tennis ball (when taking samples) you can bring down tonnes of dirt, not trying to discourage you mate, just letting you know of some of the dangers associated with hacking into remenant pillars, wether they be 10 feet down, or 1000 feet down.

I've been sketching some idea's on how to shore the shaft and rework shallow alluvial diggings. The shoring system has to be removable. The concern I have is what you mentioned above Dwt. If the side walls give, the shoring system will hold however will become a permanent fixture.
This would result in most likely a loss, unless of course a 100oz lump is recovered.

 

[loamer]

Couple of readings I have found that sounds similar to the area described. This comes from an area that gets no attention so I'll leave the names of places out, I have yet to hit it either but the quotes are as written:

"This ancient river was known as the XXXXX Lead, and the mullock heaps beside the old mine sites are composed of large round white stones and gravel from the river bed. But because it was a buried river with a thick bed of porous gravel it collected huge quantities of underground water..."

".... and the rolling of stones being dumped, washed, sluiced and tumbled around....." (when discussing the noise factor, but the description is a very interesting clue.)

"it did not take them (the diggers) long to realise the gold was buried under the embankments...... and smaller rushes broke out where diggers found the places the creek crossed the gold reefs"

Now, this is all happening in a very small area - we have an ancient stream bed (a secondary deposit) close to gold reefs (primary deposits) with ancient alluvial beds, more recent beds with water and eluvial gold. I might add, this area is quite elevated, even for Victoria.

So, as described by a couple of folk above, it appears the rounded rocks were dumped but it appears they were washed and the results sluiced NOT crushed. The gold must, IMO, have been impregnated into the round river bed rocks due to the pressure, time and proximity to gold. Therefore, I would argue that these may indeed hold small particles of gold.

 

[20x]

The old boys weren't afraid of hard work and had the time and inclination that we seem not to. I tend to tackle things from a practical side rather than research mostly because I enjoy digging sampling and washing alot more than reading (not the sharpest tool in the shed). My suggestion would be to determine what you can gain buy not just looking at what's in front of you but by putting in a shovel and pick and do thorough sampling. The proof is in the pudding so to speak. Whilst investigating a new area I try and keep it as simple as possible, when the gold is in the pan the next move becomes an easy decision. Shallow shafts always have me questioning how many duffer holes were dug too, mostly they had only a limited space and resources to get there and into the good pay dirt.

my thoughts exactly...the pan doesn't lie!

 

[WestOstrich!]

Great post guys! I'm struggling with determining where the "bottom" is on sites that we are testing. I really would like some clarification on the white pipe clay. I have read across various docs/posts that the gold was located just above, in, or just below the white pipe clay....

In reference to the Talbot/Amherst areas was this pipe clay ALWAYS considered the "bottom" as in bedrock? If it is bedrock it is extremely decomposed, makes me wonder if it would hold gold up.

Are there cases of shallow alluvial washes below the pipe clay, or is it time to dig somewhere else when we strike this with no wash above it? Sometimes the pipe clay goes down 3m thick plus.

We are concerned with "surface" type alluvial only, not shaft mining.

If anyone can pipe up about the pipe clay, I'd really appreciate it!

Cheers.

 

[loamer]

Generally, pipeclay was the last thing out before they hit the wash. It is made up of decomposed (over many millennium) material. As for depth that varies, there is no set depth as such. Here is an interesting article from the period, carried in the Geelong papers, that tells about digging through pipeclay. What's interesting is that the gold was in pockets, as you would expect in any creek-bed either modern or ancient. So not every hole had gold, not every mullock heap has throw-outs. The reason pipeclay on mullock may contain some throw-outs is that the layers they were digging were not even and they may have taken several buckets out before realising they were in the wash. Thats also why you find relics on mullock - gear/coins/buttons dropped etc etc and bucket of spill from the hole dumped on top.

Every one selected a piece of ground, which he called his claim and set to work to dig a hole in it ; but when the bottom of the sandy layer was reached, and there seemed to be nothing but pipe-clay below. However a miner named Cavenagh determined to try an experiment,he dug through the layer of pipe-clay, when he had the good fortune to come suddenly upon several large deposits of grain gold. He had reached what had been in long past ages the bed of the creek, where, in every little hollow, for century after century, the flowing waters had gently deposited the gold which they had carried with them from the mountains.

 

[WestOstrich!]

Thanks again Loamer. Just to clarify here, I have been advised by a very experienced party that the pipe clay was generally considered as the bedrock or 'bottom'. As per the article there evidently could be other separate gold depositing events below this. Is the pipeclay 'generally' considered as bedrock that would be holding up a gold depositing event or not? You seem to suggest that this is incorrect, and that most deposits were found below the pipe clay?

 

[loamer]

Brough-Smyth (the author of the Vic prospectors bibleThe Goldfields and Mineral Districts of Vic in 1869 states "Pipeclay: A soft white clay, which is often found lying between the bedrock and the washdirt. Its thickness varies from a mere trace to many feet."

On secondary (alluvial) leads, picture the creek in ancient times. The matter that made up the pipeclay settled on top of the bedrock, the base of the creek. that's why in the majority of cases, it was the last thing out. Look at a modern creek with the bedrock then look at the leaf litter, dirt and other natural rotting matter - its above the bedrock. (This is sounding like the flintstones). This also includes the term 'rotten bedrock', that is the area above the bedrock that is the natural process of it breaking down.

Now, in this series of posts there have been many generalisations made, including by me, about the nature of layers as there are some standard rules, but not always. Each gold bearing area can be quite different. Here are some examples of various layers of the diggings as reported at the time. There is no one rule I am afraid to say, that's why you can be standing at one set of diggings with white pipeclay everywhere and the next set - zero - it was either not there, very minimal or washed away. Also, check the depths - these were considered 'shallow' and the depths today, we could not detect that deep, even with our 'Wizzatrons 10000 Multi purpose Detector Doover' - mine you, the divining chaps may have a crack. :lol: You are still better off with a big coil through these areas than an 8" baby.

 

[loamer]

Addendum to my last - these are Victorian Goldfields (not NSW, SA, WA or QLD - where the weather is always nice apparently).

 

[WestOstrich!]

Very interesting Loamer, you are a mine of information (forgive the intended pun..). I realise it is a bit ridiculous to try and get these 'how long is a piece of string' questions answered, but I have to get into it somehow..

I will try and get hold of that publication.

I promise I'll leave you alone after this but... Can you tell me what sort of event created the surface 400mm of decomposed iron stained jagged quartz material that we see over thousands of acres in a continuous sheet in Central Vic? It is just so vast that I can't imagine this was a wash, and it has no pebbles in it? Is this multiple exposed reefs at the surface decomposing and moving over the surface with gravity and overland water? I can't imagine how this material covers such a vast area if it is wash related?

Thanks for all of your help, it is much appreciated Loamer.

Cheers

 

[loamer]

Here is the answer in a nutshell:

Gold bearing (auriferous) reefs: Fractures in sedimentary rocks known as joints, are caused primarily through pressure. When they cross bedding planes they are known as faults. Quartz and other gangue minerals enter these fractures as hydrothermal solutions, impregnated with gold and sulphides. Many thousands of quartz reefs occur in the auriferous belts of Victoria, but relatively few carry gold, and in these, payable gold is usually localised.

They are broken down reefs - the stuff is everywhere as you stated. Coloured/stained means that it has been subjected to mineralisation. As stated, there are 1,000s. An old adage - gold is usually with quartz but not all quartz is with gold. If you look at the area between Dunolly and Tarnagulla, 100% quartz area - way less than 5% of the land was gold bearing with some magnificent exceptions.

You also need to know the geological periods of gold:

Victorian gold deposits have generally been regarded as Ordovician to Devonian in age and may have occurred during several different periods of mineralisation. Those in the Stawell region are found in unfossiliferous Cambrian or lower Ordovician sedimentary rocks, those in the Bendigo-Ballarat region in Ordovician sedimentary rocks, the Warrandyte gold fields in Silurian sediments, Walhalla-Woods Point in Devonian dykes, and those in the east in Ordovician sediments.

Have a look at this post - it shows one of the very few remaining (barren) quartz 'mountains'. I took the pics some time ago - the whole thing is quartz - magnificent. many people have had a crack, dollyed it up and a big fat ZERO.
https://www.prospectingaustralia.com/forum/viewtopic.php?id=2115

 

[WestOstrich!]

Thanks Loamer, I just want to get away from this desk and swing a pick now!...

 

[loamer]

Quartz in Victoria.

Quartz and gold trivia

 

[Fox]

Addendum to my last - these are Victorian Goldfields (not NSW, SA, WA or QLD - where the weather is always nice apparently).

G'day Loamer, I am in the Vic goldfields at present and have noticed a lot of similarities with the Geology of NE Tasmania. Our gold bearing host rocks are primarily Ordovician to Silurian/ Devonian in age and underlain or intruded by Devonian Granitoids.
Deep leads are often covered with Tertiary Basalts or sediments.
Thanks for your interesting and informative posts, mate.
I have learnt a lot from them.
Regards, Fox