Difference Between Shallow Workings And Shallow Leads.

Prospecting Australia

Help Support Prospecting Australia:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
From my understanding a shallow lead is generally the source for the shallow workings. Get out to the place where your research is heading and have a look around. Also research the current status of the area to guide you in staying legal.
 
The workings on shallow leads (and surface gold) are "shallow workings" - simply terminology. However the term shallow lead is applied to anything up to about 30 m deep, and at depths of many metres these require a different approach. The particular "shallow workings" that are good for surface gold accessible to detectors are those where gold is almost at surface.

Imagine a quartz reef that is shedding its gold into the soil. The gold migrates downhill with gravity and rain and tends to start concentrating it in a shallow nearby gully, and water washes it down the shallow gully and out onto the flat below (usually channels in the flat, less so in arid areas). All great areas to detect.

Imagine there are floods on the flatter areas and clay and sand from the floods covers the gold-bearing gullies on gentle slopes and the flats. The gold-bearing gravels may not be washed away, they will simply be buried under the later clay. The same thing can occur in a single gully on a bit of sloping hillside, simply because with time no more gold is coming from the reef further up the hill, but sand and clay coming down the gully buries the initial gold-bearing gravels to greater and greater depth (gold invariably concentrates best in gravels located directly on older bedrock). There are other reasons for this as well - often the erosion of gold-bearing quartz reefs starts when the reefs are first exposed at surface during the first uplift of the area (fault uplift in earthquakes) - as the hills wear away the area becomes less hilly, erosion is less active and the gold input to gravels in gullies decreases. Also that gold already in the gullies works its way down to bedrock with time because the specific gravity of gold is so much higher than that of quartz sand or pebbles (nearly twice the SG of lead).

Now the first prospectors came along and initially find gold at or within tens of centimetres of surface in the upper parts of gullies and in soil around the reef. As they mine the gravels down the gully, they can initially access all the gravel by trenching etc, and turn everything over with picks and shovels, but as gold-bearing gravel gets deeper farther down the gully, they have to dig shafts at intervals to get through unmineralised clay, sand and sometimes barren gravel to get to the deeper gravel on bedrock that these other rocks conceal. They then go down their shafts and tunnel in the gold-bearing gravels between their shafts. Gradually the shafts have to get deeper to access the gold, and more expensive in time and money, so they dig shafts further apart and make the tunnels between their shafts longer (and often more dangerous because they were tunnelling entirely through wet unconsolidated gravel for long distances). They would now be said to be working a shallow lead. Often this was in areas of topographically lower relief (flattish areas - although sometimes later earthquakes uplift these flattish areas and new gullies start to form in them and erode the old gold-bearing gravels).

Ultimately they would get very deep, partly because basalt flows later flowed down the larger valleys and buried the clay, sand and gravel of the older valleys. This often caused a lull in mining for up to a decade, because it required syndicate or company finance to dig the deep shafts now required, which needed explosives, close-spaced timbering and powerful water pumps. This was often below 30 m (up to more than 150 m depth) and these were called deep leads. Often in these they would sink right through everything and into bedrock and tunnel in bedrock beneath the lead gravels, putting up rises at regular levels and then secondary tunnels in the overlying gravel ("panels") from which the ore was extracted. That way in a collapse of the gravels they had not lost all the mine workings (shafts were often many hundreds of metres apart), just the local gravels around a rise. Even if the mine flooded with an inrush of water, they could often put on a larger pump then just block off access to the rise that the water was pouring down - their main access tunnels could be revived and further rises developed up into the gravels where not so wet (they would test by drilling up into the gravels to test their water content). Dangerous work - during the gold rush 30 men per month were dying on the Ballarat goldrushes in mining accidents.

Now you and your mates come along in the 21st Century. You prospect the upper parts of gullies where everything looks turned over and have fair success. You follow the gully downhill, it flattens, and now you see separate shafts separated by what looks like (but isn't at depth) unmined ground. At this point the only area usually worth detecting is the mullock around the shaft collars, because this is the only material that came from deep enough to contain gold (and got spilt around the collars or dumped immediately at surface because it was mostly lower-grade than the high-grade gravel they were interested in - but they still missed isolated nuggets because they did not wash such gravel). As the shafts get further apart, these shaft collars become absolutely the only places you will detect gold (there is also slight potential on washed pebble dumps that have been treated). Once you see basalt on the mine dumps you are commonly wasting your time, although if there is a fair bit of gravel mixed with this lava it might be worth a try.

Learn some geology and increase your chances 1000%, I often see people working all over flats with their metal detectors when I know the lead is 20 m deep and they are wasting their time anywhere except on the shaft collars (or pebble dumps from which most gold has been washed - really big nuggets were sometimes missed there because they sat with cobbles on the top of the mesh they screened the gravel through before washing it to separate gold (but remember that mining was labour intensive - often hundreds of people on single deep lead mines, including hungry eagle-eyed young boys working for a pittance).
 
My understanding of a lead is an old creek/river that has been covered over from lava etc, regardless of depth, 100m to 300mm. Leaving basalt etc like a concrete slab over the old bed. then the creek/river may change course.
And ancient river wash is where the creek/river once was. Both are alluvial deposits.
Feel free to comment!
 
goldierocks said:
The workings on shallow leads (and surface gold) are "shallow workings" - simply terminology. However the term shallow lead is applied to anything up to about 30 m deep, and at depths of many metres these require a different approach. The particular "shallow workings" that are good for surface gold accessible to detectors are those where gold is almost at surface.

Imagine a quartz reef that is shedding its gold into the soil. The gold migrates downhill with gravity and rain and tends to start concentrating it in a shallow nearby gully, and water washes it down the shallow gully and out onto the flat below (usually channels in the flat, less so in arid areas). All great areas to detect.

Imagine there are floods on the flatter areas and clay and sand from the floods covers the gold-bearing gullies on gentle slopes and the flats. The gold-bearing gravels may not be washed away, they will simply be buried under the later clay. The same thing can occur in a single gully on a bit of sloping hillside, simply because with time no more gold is coming from the reef further up the hill, but sand and clay coming down the gully buries the initial gold-bearing gravels to greater and greater depth (gold invariably concentrates best in gravels located directly on older bedrock). There are other reasons for this as well - often the erosion of gold-bearing quartz reefs starts when the reefs are first exposed at surface during the first uplift of the area (fault uplift in earthquakes) - as the hills wear away the area becomes less hilly, erosion is less active and the gold input to gravels in gullies decreases. Also that gold already in the gullies works its way down to bedrock with time because the specific gravity of gold is so much higher than that of quartz sand or pebbles (nearly twice the SG of lead).

Now the first prospectors came along and initially find gold at or within tens of centimetres of surface in the upper parts of gullies and in soil around the reef. As they mine the gravels down the gully, they can initially access all the gravel by trenching etc, and turn everything over with picks and shovels, but as gold-bearing gravel gets deeper farther down the gully, they have to dig shafts at intervals to get through unmineralised clay, sand and sometimes barren gravel to get to the deeper gravel on bedrock that these other rocks conceal. They then go down their shafts and tunnel in the gold-bearing gravels between their shafts. Gradually the shafts have to get deeper to access the gold, and more expensive in time and money, so they dig shafts further apart and make the tunnels between their shafts longer (and often more dangerous because they were tunnelling entirely through wet unconsolidated gravel for long distances). They would now be said to be working a shallow lead. Often this was in areas of topographically lower relief (flattish areas - although sometimes later earthquakes uplift these flattish areas and new gullies start to form in them and erode the old gold-bearing gravels).

Ultimately they would get very deep, partly because basalt flows later flowed down the larger valleys and buried the clay, sand and gravel of the older valleys. This often caused a lull in mining for up to a decade, because it required syndicate or company finance to dig the deep shafts now required, which needed explosives, close-spaced timbering and powerful water pumps. This was often below 30 m (up to more than 150 m depth) and these were called deep leads. Often in these they would sink right through everything and into bedrock and tunnel in bedrock beneath the lead gravels, putting up rises at regular levels and then secondary tunnels in the overlying gravel ("panels") from which the ore was extracted. That way in a collapse of the gravels they had not lost all the mine workings (shafts were often many hundreds of metres apart), just the local gravels around a rise. Even if the mine flooded with an inrush of water, they could often put on a larger pump then just block off access to the rise that the water was pouring down - their main access tunnels could be revived and further rises developed up into the gravels where not so wet (they would test by drilling up into the gravels to test their water content). Dangerous work - during the gold rush 30 men per month were dying on the Ballarat goldrushes in mining accidents.

Now you and your mates come along in the 21st Century. You prospect the upper parts of gullies where everything looks turned over and have fair success. You follow the gully downhill, it flattens, and now you see separate shafts separated by what looks like (but isn't at depth) unmined ground. At this point the only area usually worth detecting is the mullock around the shaft collars, because this is the only material that came from deep enough to contain gold (and got spilt around the collars or dumped immediately at surface because it was mostly lower-grade than the high-grade gravel they were interested in - but they still missed isolated nuggets because they did not wash such gravel). As the shafts get further apart, these shaft collars become absolutely the only places you will detect gold (there is also slight potential on washed pebble dumps that have been treated). Once you see basalt on the mine dumps you are commonly wasting your time, although if there is a fair bit of gravel mixed with this lava it might be worth a try.

Learn some geology and increase your chances 1000%, I often see people working all over flats with their metal detectors when I know the lead is 20 m deep and they are wasting their time anywhere except on the shaft collars (or pebble dumps from which most gold has been washed - really big nuggets were sometimes missed there because they sat with cobbles on the top of the mesh they screened the gravel through before washing it to separate gold (but remember that mining was labour intensive - often hundreds of people on single deep lead mines, including hungry eagle-eyed young boys working for a pittance).
Click to expand...

So much to be learned! Your knowledge is priceless, I have a long way to go yet but your reply has helped immensely.

The area Im thinking of going is Waanyarra and camping on some of the areas. How would I do here do you think?
 
VicGoldHunter said:
goldierocks said:
The workings on shallow leads (and surface gold) are "shallow workings" - simply terminology. However the term shallow lead is applied to anything up to about 30 m deep, and at depths of many metres these require a different approach. The particular "shallow workings" that are good for surface gold accessible to detectors are those where gold is almost at surface.

Imagine a quartz reef that is shedding its gold into the soil. The gold migrates downhill with gravity and rain and tends to start concentrating it in a shallow nearby gully, and water washes it down the shallow gully and out onto the flat below (usually channels in the flat, less so in arid areas). All great areas to detect.

Imagine there are floods on the flatter areas and clay and sand from the floods covers the gold-bearing gullies on gentle slopes and the flats. The gold-bearing gravels may not be washed away, they will simply be buried under the later clay. The same thing can occur in a single gully on a bit of sloping hillside, simply because with time no more gold is coming from the reef further up the hill, but sand and clay coming down the gully buries the initial gold-bearing gravels to greater and greater depth (gold invariably concentrates best in gravels located directly on older bedrock). There are other reasons for this as well - often the erosion of gold-bearing quartz reefs starts when the reefs are first exposed at surface during the first uplift of the area (fault uplift in earthquakes) - as the hills wear away the area becomes less hilly, erosion is less active and the gold input to gravels in gullies decreases. Also that gold already in the gullies works its way down to bedrock with time because the specific gravity of gold is so much higher than that of quartz sand or pebbles (nearly twice the SG of lead).

Now the first prospectors came along and initially find gold at or within tens of centimetres of surface in the upper parts of gullies and in soil around the reef. As they mine the gravels down the gully, they can initially access all the gravel by trenching etc, and turn everything over with picks and shovels, but as gold-bearing gravel gets deeper farther down the gully, they have to dig shafts at intervals to get through unmineralised clay, sand and sometimes barren gravel to get to the deeper gravel on bedrock that these other rocks conceal. They then go down their shafts and tunnel in the gold-bearing gravels between their shafts. Gradually the shafts have to get deeper to access the gold, and more expensive in time and money, so they dig shafts further apart and make the tunnels between their shafts longer (and often more dangerous because they were tunnelling entirely through wet unconsolidated gravel for long distances). They would now be said to be working a shallow lead. Often this was in areas of topographically lower relief (flattish areas - although sometimes later earthquakes uplift these flattish areas and new gullies start to form in them and erode the old gold-bearing gravels).

Ultimately they would get very deep, partly because basalt flows later flowed down the larger valleys and buried the clay, sand and gravel of the older valleys. This often caused a lull in mining for up to a decade, because it required syndicate or company finance to dig the deep shafts now required, which needed explosives, close-spaced timbering and powerful water pumps. This was often below 30 m (up to more than 150 m depth) and these were called deep leads. Often in these they would sink right through everything and into bedrock and tunnel in bedrock beneath the lead gravels, putting up rises at regular levels and then secondary tunnels in the overlying gravel ("panels") from which the ore was extracted. That way in a collapse of the gravels they had not lost all the mine workings (shafts were often many hundreds of metres apart), just the local gravels around a rise. Even if the mine flooded with an inrush of water, they could often put on a larger pump then just block off access to the rise that the water was pouring down - their main access tunnels could be revived and further rises developed up into the gravels where not so wet (they would test by drilling up into the gravels to test their water content). Dangerous work - during the gold rush 30 men per month were dying on the Ballarat goldrushes in mining accidents.

Now you and your mates come along in the 21st Century. You prospect the upper parts of gullies where everything looks turned over and have fair success. You follow the gully downhill, it flattens, and now you see separate shafts separated by what looks like (but isn't at depth) unmined ground. At this point the only area usually worth detecting is the mullock around the shaft collars, because this is the only material that came from deep enough to contain gold (and got spilt around the collars or dumped immediately at surface because it was mostly lower-grade than the high-grade gravel they were interested in - but they still missed isolated nuggets because they did not wash such gravel). As the shafts get further apart, these shaft collars become absolutely the only places you will detect gold (there is also slight potential on washed pebble dumps that have been treated). Once you see basalt on the mine dumps you are commonly wasting your time, although if there is a fair bit of gravel mixed with this lava it might be worth a try.

Learn some geology and increase your chances 1000%, I often see people working all over flats with their metal detectors when I know the lead is 20 m deep and they are wasting their time anywhere except on the shaft collars (or pebble dumps from which most gold has been washed - really big nuggets were sometimes missed there because they sat with cobbles on the top of the mesh they screened the gravel through before washing it to separate gold (but remember that mining was labour intensive - often hundreds of people on single deep lead mines, including hungry eagle-eyed young boys working for a pittance).
Click to expand...

So much to be learned! Your knowledge is priceless, I have a long way to go yet but your reply has helped immensely.

The area Im thinking of going is Waanyarra and camping on some of the areas. How would I do here do you think?
Click to expand...
So long since I have worked there that one should check all access legalities (I don't know the nature of those extensive reserves). Used to be good. Tarnagulla had one of Victoria's richest gold-quartz mine for a bit, averaged 3 oz per tonne. Everyone knows the nuggets of Poseidon (but boy, has that been done over since).

Here is a cross-section of a deep lead alluvial gold mine. You can see the problem - only the gravels at the bottom have significant gold, so there are few places at surface where you can detect. On the right are older, uplifted gravels (an ideal place to detect). Where the leads are shallower they may lack the basalt on top, but in flatter areas it is still up to 30 m down to the top of the gold-bearing gravel (so same problem - detecting on those overlying clays, or around the modern river, will achieve little). An important point - nearly all significant alluvial gold in Victoria was NOT associated with modern rivers - for reasons you can see, many big rivers were quite barren e,g, the Loddon River). Hope that helps. A few were productive (eg the Lerderderg) but the overall ounces out of the river itself even there was miniscule compared with surrounding shallow leads and quartz veins (it cut a gorge so cut through gold-quartz veins in bedrock, which put some gold into the modern river). Most deposits were formed in rivers that existed 22 million years ago (those shown as uplifted are probably 35 million years (My) old - not as rich as the 22 My group, nor as extensive, but still locally productive in fields like Ararat and Stawell.

1555832388_deep_lead_gravel.jpg
 
Goldierocks wrote:

"However the term shallow lead is applied to anything up to about 30 m deep" I always wondered that, thanks :Y:

"Now the first prospectors came along and initially find gold at or within tens of centimetres of surface in the upper parts of gullies and in soil around the reef. As they mine the gravels down the gully, they can initially access all the gravel by trenching etc, and turn everything over with picks and shovels, but as gold-bearing gravel gets deeper farther down the gully, they have to dig shafts at intervals to get through unmineralised clay, sand and sometimes barren gravel to get to the deeper gravel on bedrock that these other rocks conceal. They then go down their shafts and tunnel in the gold-bearing gravels between their shafts. Gradually the shafts have to get deeper to access the gold, and more expensive in time and money, so they dig shafts further apart and make the tunnels between their shafts longer (and often more dangerous because they were tunnelling entirely through wet unconsolidated gravel for long distances). They would now be said to be working a shallow lead. Often this was in areas of topographically lower relief (flattish areas - although sometimes later earthquakes uplift these flattish areas and new gullies start to form in them and erode the old gold-bearing gravels)." It was all interesting. Found this section particularly so.

Thanks for your explanations ;)
 
Goldierocks also wrote

"Learn some geology and increase your chances 1000%". I absolutely agree and have tried to do just that but...jeez I struggle with all of the convoluted terminology. To have someone like yourself put it into laymen terms and also be able to link it with what the old timers did, why they did it and the remains of that which we now see in the goldfields. Priceless :100: :trophy:
 
Thanks. I try to spell it out simply.

A lot is simple, just the words used can isolate people from reading science. There is a reason - geologists (all scientists) need to know EXACTLY what another geologist is saying. They invent new words continuously because their definitions are very exact so that no confusion results between geologists (already existing words often have ambiguous meanings). Many early British geologists understood Latin, and some words are Latin. Ages of rocks can be like that - the oldest are Archean (think archaic - ancient rocks). Carboniferous - the rocks of an age that contained most European coal deposits (i.e. carbon). Many were named after areas or the tribes who lived in them - the Ordovices and Silures give their names to the Ordovician and Silurian - Cambria (Cambrian) is in wales, Perm in Russia (Permian), Devon in England (Devonian), Jura in Switzerland (Jurassic) - the places where rocks of these ages were first described. Latin was used by chemists to name the elements and give them symbols -aurum for gold (Au), cuprum for copper (Cu), argentum for silver (Ag), plumbum for lead (Pb). So geologists talk of auriferous rocks - gold bearing. The three main groups of rocks are igneous (Latin = ignis or fire, as in ignite). Those formed from hot molten (fiery) rock. Sedimentary - deposited as a sediment like clay and sand. From Latin sedimentum (to settle or settle down) - think of the word sedentary. Metamorphic rocks - any rock heated or subjected to high pressure AFTER it formed = Latin meta =changed, morph = form, so a rock that has had its form changed (we use words like pseudomorph as well - false form, pseudonym = false name). Or we morph shapes.

Once you recognise this it becomes a bit less daunting. First year geology students also find it difficult. Minerals are often named after people but also elements and commonly end in -ite. Cuprite - copper mineral. Argentite - silver mineral. Chalcos is short for "ore former" (Greek) and again pyrite from pyros (fire). So pyrite and chalcopyrite. Azurite = blue mineral as in azure skies. Hence fireworks are pyrotechnics. Malachite is Greek from malakhe, after the green leaves of the mallow plant. Basalt is a corruption of an Ethiopian word for very hard stone, granite from Latin granum which refers to the grainy appearance of the rock (we also use this for grains like wheat, which we keep in a granary). Marble from the Greek word marmaros meaning white stone. Minerals are also named after people - gierite after Bruno Gier (a mineralogist), curite (after Madame Curie who discovered radioactivity), stottite after Charlie Stott (a mine manager) - two are named after my old friends (johninnesite, tredouxite). Also place names coloradoiite (obvious), maldonite (Maldon goldfield in Victoria). Not so complicated.

So simple words, but derived from a Latin or other language. English is a Germanic language in its structure, but 60% of the words in it are from Latin (the Romans lived in England for 400 years after all). Many mining words come from other languages, including Cornish and German (important mining areas). You may have heard the term plat, where you get off at a level in a shaft. Means flat (eg German, Dutch = Holland is a platteland). Crib was used by Cornish for a box - that you kept food in - underground the crib house became the area you ate lunch.
 
goldierocks said:
The workings on shallow leads (and surface gold) are "shallow workings" - simply terminology. However the term shallow lead is applied to anything up to about 30 m deep, and at depths of many metres these require a different approach. The particular "shallow workings" that are good for surface gold accessible to detectors are those where gold is almost at surface.

Imagine a quartz reef that is shedding its gold into the soil. The gold migrates downhill with gravity and rain and tends to start concentrating it in a shallow nearby gully, and water washes it down the shallow gully and out onto the flat below (usually channels in the flat, less so in arid areas). All great areas to detect.

Imagine there are floods on the flatter areas and clay and sand from the floods covers the gold-bearing gullies on gentle slopes and the flats. The gold-bearing gravels may not be washed away, they will simply be buried under the later clay. The same thing can occur in a single gully on a bit of sloping hillside, simply because with time no more gold is coming from the reef further up the hill, but sand and clay coming down the gully buries the initial gold-bearing gravels to greater and greater depth (gold invariably concentrates best in gravels located directly on older bedrock). There are other reasons for this as well - often the erosion of gold-bearing quartz reefs starts when the reefs are first exposed at surface during the first uplift of the area (fault uplift in earthquakes) - as the hills wear away the area becomes less hilly, erosion is less active and the gold input to gravels in gullies decreases. Also that gold already in the gullies works its way down to bedrock with time because the specific gravity of gold is so much higher than that of quartz sand or pebbles (nearly twice the SG of lead).

Now the first prospectors came along and initially find gold at or within tens of centimetres of surface in the upper parts of gullies and in soil around the reef. As they mine the gravels down the gully, they can initially access all the gravel by trenching etc, and turn everything over with picks and shovels, but as gold-bearing gravel gets deeper farther down the gully, they have to dig shafts at intervals to get through unmineralised clay, sand and sometimes barren gravel to get to the deeper gravel on bedrock that these other rocks conceal. They then go down their shafts and tunnel in the gold-bearing gravels between their shafts. Gradually the shafts have to get deeper to access the gold, and more expensive in time and money, so they dig shafts further apart and make the tunnels between their shafts longer (and often more dangerous because they were tunnelling entirely through wet unconsolidated gravel for long distances). They would now be said to be working a shallow lead. Often this was in areas of topographically lower relief (flattish areas - although sometimes later earthquakes uplift these flattish areas and new gullies start to form in them and erode the old gold-bearing gravels).

Ultimately they would get very deep, partly because basalt flows later flowed down the larger valleys and buried the clay, sand and gravel of the older valleys. This often caused a lull in mining for up to a decade, because it required syndicate or company finance to dig the deep shafts now required, which needed explosives, close-spaced timbering and powerful water pumps. This was often below 30 m (up to more than 150 m depth) and these were called deep leads. Often in these they would sink right through everything and into bedrock and tunnel in bedrock beneath the lead gravels, putting up rises at regular levels and then secondary tunnels in the overlying gravel ("panels") from which the ore was extracted. That way in a collapse of the gravels they had not lost all the mine workings (shafts were often many hundreds of metres apart), just the local gravels around a rise. Even if the mine flooded with an inrush of water, they could often put on a larger pump then just block off access to the rise that the water was pouring down - their main access tunnels could be revived and further rises developed up into the gravels where not so wet (they would test by drilling up into the gravels to test their water content). Dangerous work - during the gold rush 30 men per month were dying on the Ballarat goldrushes in mining accidents.

Now you and your mates come along in the 21st Century. You prospect the upper parts of gullies where everything looks turned over and have fair success. You follow the gully downhill, it flattens, and now you see separate shafts separated by what looks like (but isn't at depth) unmined ground. At this point the only area usually worth detecting is the mullock around the shaft collars, because this is the only material that came from deep enough to contain gold (and got spilt around the collars or dumped immediately at surface because it was mostly lower-grade than the high-grade gravel they were interested in - but they still missed isolated nuggets because they did not wash such gravel). As the shafts get further apart, these shaft collars become absolutely the only places you will detect gold (there is also slight potential on washed pebble dumps that have been treated). Once you see basalt on the mine dumps you are commonly wasting your time, although if there is a fair bit of gravel mixed with this lava it might be worth a try.

Learn some geology and increase your chances 1000%, I often see people working all over flats with their metal detectors when I know the lead is 20 m deep and they are wasting their time anywhere except on the shaft collars (or pebble dumps from which most gold has been washed - really big nuggets were sometimes missed there because they sat with cobbles on the top of the mesh they screened the gravel through before washing it to separate gold (but remember that mining was labour intensive - often hundreds of people on single deep lead mines, including hungry eagle-eyed young boys working for a pittance).
Click to expand...

This is fantastic. Thanks for sharing goldierocks.
 
Northeast said:
Goldierocks also wrote

"Learn some geology and increase your chances 1000%". I absolutely agree and have tried to do just that but...jeez I struggle with all of the convoluted terminology. To have someone like yourself put it into laymen terms and also be able to link it with what the old timers did, why they did it and the remains of that which we now see in the goldfields. Priceless :100: :trophy:
Click to expand...

I agree totaly, the book terminology is mind boggling as there can be 3 words per sentence you need to google and the lack of pictures is what i really struggle with , by the time i read a page of geology then try find picture examples of the minerals or formations etc i have lost all track of what they are saying.
 
aussiefarmer said:
Northeast said:
Goldierocks also wrote

"Learn some geology and increase your chances 1000%". I absolutely agree and have tried to do just that but...jeez I struggle with all of the convoluted terminology. To have someone like yourself put it into laymen terms and also be able to link it with what the old timers did, why they did it and the remains of that which we now see in the goldfields. Priceless 💯 🏆
Click to expand...

I agree totally, the book terminology is mind boggling as there can be 3 words per sentence you need to google and the lack of pictures is what i really struggle with , by the time i read a page of geology then try find picture examples of the minerals or formations etc i have lost all track of what they are saying.
Click to expand...

I can fully appreciate that problem - much of the first year of a geology degree involves learning terminology. But possibly you are reading the wrong books. First you need to get a very basic background in geology overall - the ideas of igneous, sedimentary and metamorphic rocks and folding (deformation) of rocks - faults and folds. Then understand the difference between a chemical element (about 92 occur naturally), componds (=minerals) and rocks. Elements combine with each other to form chemical compounds. For example copper and oxygen combine to form the compound copper oxide - copper, oxygen and carbon combine to form the compound copper carbonate.

Chemical compounds that are not organic and that occur naturally in nature are what we call minerals - because they often crystallize slowly this can result in large and beautiful crystals. Each mineral is defined by two things - not just its chemical composition but also its crystal structure (the way its atoms are arranged internally within the crystal). So graphite and diamond are both the element carbon, but are different minerals because they have quite different crystal structures (which gives them different hardness, colour, lustre, specific gravity etc.). Calcite and aragonite are both calcium carbonate, but because they have different crystal structures they are two different minerals. We also simplify terminology by grouping minerals with related characteristics - the pyroxene group includes many minerals (augite, diopside), similarly the amphibiole group (hornblende, tremolite, actinolite, even blue asbestos), or the garnet group (almandite, grossularite etc.), or the epidote group (epidote, zoisite, clinozoisite).

Gemstones and precious stones are simply pretty minerals. The names are sometimes not made up by geologists but can be invented by dealers or companies as an aid to marketing. Geologists invented names like ruby and sapphire for red and blue versions of the mineral corundum, and emerald and aquamarine for beryl minerals that have those colours. But the list is endless - quartz gem minerals (citrine, cairngorm, amethyst, agate, chalcedony), or recent additions (tanzanite - a beautiful form of epidote from Tanzania, tsavorite - beautiful green garnet from Tsavora valley, also in that country).

Rocks are mostly just substances built of more than one mineral. So granite is usually biotite+feldspar+quartz (but never olivine) - basalt is often olivine+pyroxene+feldspar (but never quartz). However some rocks are simply made of huge numbers of grains of a single mineral (sandstone is quartz grains, limestone is calcite grains). So you could say that almost all rocks are built of multiple grains of minerals.

Then you need to understand that some minerals separate out of molten rocks, but many crystallize from water solutions. So many non-geologists think that gold-bearing quartz veins are "intruded" into faults in rocks as some sort of molten goo. They do not - they simply crystallize slowly on both walls of the fault from a dilute hot water solution that is flowing through the open fault cavity, until finally crystals grow all the way to the centre giving a sealed vein, and further flow of water is blocked. That is why you often see crystals and open cavities in the centre of quartz veins - bits that were not completely blocked and closed off. If you watched a quartz vein forming, you would see an open fracture, a layer of quartz on each wall, and very hot clear water pumping through between the walls.

Sometimes minerals crystallize from quite cool water (but may still be large crystals), and other minerals are altered by rain and atmosphere close to surface to crystallize as new minerals. So a quartz vein that contains copper sulphide minerals at depth (e.g. chalcopyrite, chalcocite, covellite) will alter near surface by reaction with oxygen in the atmosphere to form things like copper oxide (cuprite) or copper sulphate (chalcanthite); they also react with carbon dioxide in the atmosphere to form copper carbonates like malachite and azurite. So these minerals form at the top of ore bodies, close to surface. Many prospectors know that ironstone and quartz often occur together - one reason is because the quartz probably contains pyrite (iron sulphide) at depth, but this reacts with oxygen in the atmosphere near surface to give iron oxide (eg the mineral limonite or goethite).

Many people assume that gold cannot dissolve in near-surface cold water, Incorrect. In desert areas, the water is often highly saline (e.g. tens of percent dissolved salt - ordinary table salt in composition). Gold dissolves readily in this near the surface, where there is also plenty of atmospheric oxygen. The dissolved gold then moves through the soil in groundwater and weathered rock until it meets up with some carbon or iron, then it dumps out again as metallic gold, sometimes as nuggets (so some gold nuggets actually form in the soil). The original gold may have a lot of contained silver, but the new gold in the soil is almost pure gold.
 
but even if a mine was a deeper lead mine you can always detect on the mullock heaps just be careful of shafts,
 
indi said:
but even if a mine was a deeper lead mine you can always detect on the mullock heaps just becareful of shafts,
Click to expand...
As I explained, you can but it is less likely to be useful. If you get your eye in, you will find three dumps around a deep lead shaft. The mullock dump, consisting of rock the shaft passed through. This is often almost all basalt with so little gravel it is of little use (being a deep and therefore large mine, they usually had an efficient way of removing gravel from the shaft vicinity when it got to surface - less so with shallow leads where stuff got spilled and wasted or dumped next to the shaft if it was considered low grade). Second is the pebble dump - the pebbles screened out during washing - no gold except very large nuggets they missed because it has been through a sieve (so not very useful). Thirdly. a lower dump that was originally the slums dam, now consisting of sand (originally this had a wall around it, now rotted away, so it now looks like a low dump). This has had the gold washed out of it. I would not detect deep leads.

Hope that clarifies....
 
Thankyou goldierocks for your in depth explanations, for newbie like me this is very helpful. I will be relying on my wife, she studied geology many years ago, hopefully she can remember it.
 
When knowledge resides within the world of academia and the secret languages of jargon and acronyms then the opportunity to learn can be lost.
Good on you Goldierocks for sharing your knowledge in a meaningful way. Like myself, I reckon a lot people read your responses beginning to end.
Cheers.
Martyz
 
Quote Goldierocks,

"Many people assume that gold cannot dissolve in near-surface cold water, Incorrect. In desert areas, the water is often highly saline (e.g. tens of percent dissolved salt - ordinary table salt in composition). Gold dissolves readily in this near the surface, where there is also plenty of atmospheric oxygen. The dissolved gold then moves through the soil in groundwater and weathered rock until it meets up with some carbon or iron, then it dumps out again as metallic gold, sometimes as nuggets (so some gold nuggets actually form in the soil). The original gold may have a lot of contained silver, but the new gold in the soil is almost pure gold."

I remember seeing a picture of a nail that was found gold plated in a creek near an old gold field in NZ.
 

Similar threads

G
Detecting the Flats beside workings
Replies
3
Views
1K
Goldfield Joe
G
mbasko
  • Locked
  • Sticky
✅ Metal Detecting for Gold help threads - Where, Why, How.......?
Replies
0
Views
2K
mbasko
mbasko
X
Detectors for Big Deep gold versus Detectors for Small Shallow gold
Replies
5
Views
1K
PhaseTech
PhaseTech
W
Roadside detecting is it legal?
Replies
3
Views
771
Whoey
W
T
Hunting around in the hills behind Cairns
Replies
4
Views
293
grubstake
grubstake

Latest posts

Top