Indicators and Quartz reefs

Just wondering if any of you folks have ever came across an 'indicator' line or even seen one while out prospecting? (Reef / hard rock mining)
It had me stumped for awhile how if - most quartz (not all) reefs run roughly in a NNW - SSE in Victoria and 'Indicator' lines run in this same direction, how could they meet ?
Because when a indicator line intersects a quartz reef gold is found.
I was then informed by a knowledgeable chap that most quartz reefs have 'spurs, fingers, veins, offshoots' which formed outwards and away from the main reef in any direction, it is these that and 'indicator line' could meet. The old fellas called these smaller quartz offshoots 'Leaders' because they 'led' them to the main reef.

I did find once a quartz specimen water-worn, the size of a emu egg which had a small black 'graphite' intrusion (like a pencil lead) in the side of it, my detector said there was something inside. I broke it open and right in the center of the quartz was a small gold nugget the size of a match head, it was completely sealed in. I went back and searched the area but could not find another like it. Thinking back I should have kept it whole.

Scott .

Gday Scott


When you say "indicator lines" what exactly are you refering to?, do you mean fault lines or shear zones, as being visible indicators of the past activity of the area.

cheers

stayyerAU

From my understanding in quartz reef mining, the miners came across these Indicator lines which were small veins of pyrites or thin layers of slate. Around Maryborough, the formation was known as Book Leaf slate (because it resembled the pages of a book). Further to the west (Ararat) the Indicator line resembled a pencil line drawn through the earth.
These lines were no wider than the width of a man's finger.

Scott.

i am probly wrong a indicator to me is where the old blokes had dug a deep shaft normaly at the top of a hill down to the right deph then at aprox point down the hill before the gully thats where thay started prospecting. nornaly you will see them and all around the hill at that point there are digs till thay find the right side of the hill this is only my thinking on indicators if any body has any other thoughts on this it would be great cheers buck

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This is from the Dept of Mines 1903 Bulletins of the Geological Survey of Victoria, No. 2 The Pyrenees Goldfield by W.M. Bradford.

Thanks Buck and StayyerAU for your replies.
Yes, there are quiet a few 'indicators' that gold is present, even recent ones like holes left by fellow gold detectorists, native trees like the Cherry Bullart trees and burnt quartz.
This image may help. I have not ever seen an 'indicator' line but would like too.
Scott.

Just wondering how can native tree's be an indicator for gold brearing area?

Hi scott. My understanding is that an indicator (in 1800's mining terms) is any mineral or geological feature, eg a specific type of vein, fault, that is known to indicate the presence of gold in that area(the indicator often contains small traces of gold along its length). The idea is they know that a certain coloured/mineralized rock bed/vein produces gold in that area. They simply follow that layer (usually a thin vertically bedded layer) either on the surface of the ground or by mining hoping to find a gold rich section.

In a real sense it usually involved looking for a specific sized, mineralized & textured quartz vein by following the line of strike from existing spots where gold was found in the vein (or often a swarm of veins).

In modern terms very specific minerals or combinations of minerals are used by mining companies to hone in on desired mineralisation sites. eg there are specific minerals that indicate there are/or were kimberlite pipes around.

Garretace- Certain trees/plants prefer certain soil/nutrient/Ph conditions. Mineralisation can result in different vegetation growing on it. Even the health of the trees can be effected by the minerals in the soil. Through false colour/infrared aerial and satellite imaging it is possible to detect the change in vegetation health and possible mineral target sites. I remember seeing a number of mining articles about vege showing mineralization sites however most of the papers are probably only available on the web as abstracts unless you wish to purchase them. For the prospector on the ground however i use vegetation to indicate where ground may be shallower or to follow contours around slopes at the level where gold may be found. I have heard of certain species indicating the presence of rotted out kaolin clay rich quartz veins.

Tributer

Hi All, An 'Indicator' is refered to many things now days such as, quartz with ironstone, changes in the colour of the ground, dips and changes in elevations of slope, changes in rock types etc etc.

The true indicator or where the term indicator came from was in Ballarat where a father and son were mining and the 15 year old son discovered or realised that the thin black line (as described in the first post here) was associated with gold deposits. I am under the impression that this black line in carbon and filtered water etc carring gold and filtered it and this is why the gold deposits can be found here. This then beacame realised that when one found and indicator this is what they followed.

Garretace, native trees and plants can be associated with gold deposits (not in all cases) because many of these vegatations grow in highly mineralised ground only, or some grasses that will be growing in one area or clump may indicate an area that had a hollow or dip and over time has filled with wash and thus collecting gold deposits.

Cheers

All good replies to 'indicators'.
Tributer and GoldstalkerGPX 'Good on you!', both good explanations and a willingness to share your knowledge.
Thanks
Scott.

Thanks guys. I was a little unsure why native tree's would indicate a gold spot but now i no. Will keep that in mind when im out in the field!

Gday


There are many things that could be considered as indicators, but it seems that in this case the reference is to a form of indicator that was common to that particular area, and there would have been similar things that the old timers recognised in other areas.

The subject of vegetation indicating mineral deposits is very interesting, and I have noted that in some areas that I have found gold there are sometimes particular trees and shrubs that seem more abundant than they are elsewhere, not that this necessarily indicates the presence of gold but it could indicate the presence of a lot of minerals that make up the composition of the ground that these particular plants find to their liking and it allows them to thrive.

Observation is the key, the subject is known as geobotanical prospecting, and has been around forever, in the very early days ancient people like the Mayans possibly would have very closely inspected the mounds of ants and other ground boring creatures to see what the compositon was of the dirt that they had brought to the surface, just as we now inspect rabbit warrens and the like to see if they may have kicked out a nuggy or two, lots of gold has been found in this way.

There are other indicators such as the density of the scrub in particular areas indicating deeper ground, or a line of trees or shrubs following an old creek bed and fault line, when you are observing an area that is reasonably well populated with vegetation and then you can see either a line of stunted growth or areas of little or no growth then it indicates that the ground is shallow with little or no topsoil, this would indicate the possible presence of a reef just below the surface so it should be more closely inspected.

The old timers recognised many of these things and a combination of several of these features would have caused them to stop and have a closer look, and pehaps either sample the surrounding stone or carry out some loaming to see if any gold was present.

cheers


stayyerAU

this may help shed some light on the sebject

http://www.youtube.com/watch?v=lxjMWJQAgdY

It was all just a shoot of Gold off the main line to the East and no more was found but you should never disregaurd a gold bearing reef line like that one if it has had a shoot like that there would be more it is well worth a chase along the line the claim was surrended.

I think I found what could be termed an indicator some years ago

In the Minelab 170000 days I found some nice gold all over a small hill which had a deep mineshaft sunk vertically at the top of the hill.

This shaft was centred on the junction of a small quartz reef and a line of ironstone which intersected at 90 deg.
When the SD range came out the gold kept coming off this hill for some time before the pickings got thin and I started looking along the reef lines for the source. I think the old timers got the source with the shaft but about 3m away ran a very small quartz line in parallel with the main reef.

Detecting along this one day I got a nice mellow deep signal right at the intersection of the small reef and the ironstone line.
About a foot down the gold started to come out in small sharp pieces with quartz and ironstone attached to most of the bits. The gold ran vertically down the intersection of the two reefs and went down another foot before it petered out to nothing. All up 3.5 ounces came out of the one hole in detectable bits and after panning all the dirt another 2/3 of an ounce was gained.

This gold had obviously formed at both of the intersections with the small line of gold that I found possibly being an indicator of the larger source that the old timers dug up.