Alluvial Gold and Eluvial Gold
.... Knowledge That Can Help You To Make a Huge Gold Find
Just What is Primary, Alluvial Gold and Eluvial gold
Primary gold is Reef or Lode gold where the gold is still deposited in its original host rock.
There are a few theories on how gold originated but the main consensus is that the majority of gold nuggets originate from Primary gold deposits.
Alluvial Gold (Deposited by water movement) and
Eluvial gold (disintegration of rock at the site where it originates - not there through water movement)
are essentially primary gold broken down by weathering and erosion and transported by gravity or water movement over many millenia of geological time.
The landscape of Western Australia was very different millions of years ago, in fact,
prospectors would be thankful that the changes over geological time have exposed so much primary ore lodes in Western Australia.
Constant weathering, geological upheavals, redeposition of material in the WA ancient landscape over the millions of years
has lead to amazing opportunities to find gold in this state for the modern knowledgeable Gold prospector.
Gold Nuggets Do Not Like to Be Lonely
....Where You Find Gold There Will Be More
What does all this mean - basically where you find gold, or where it has been found in the past is a good indication of further gold that can be found
in that area.
It is important to understand and interpret the gold you find and the local geological environment so you can try to determine what type of gold it is, whether it is alluvial gold or eluvial gold and how it got to the spot where you found it.
These are clear Red Flashing Light signals to you that there may be a primary source of gold nearby.
Alluvial Gold and Eluvial Gold - The Important Differences That May Lead You to the Motherlode!
|Relationship to primary source of gold
- Fine gold and small nuggets Can be transported many kilometers from source of gold.
- Can be ancient alluvial gold deposits in ground lifted high above current stream levels.
Large nuggets, may be closer to primary gold source.
|How is this type of gold transported
||Moved by water through gullies, streams, creeks and rivers
Freed up from the gold source by erosion/weathering and moved by gravity downslope.|
Can be very close to the gold source if it the source has not been dispersed.
- Rounded Edges, small nuggets, flakes or gold dust
- Larger nuggets closer to the source in upper reaches of river or creek
- Finer gold further from the source or in lower reaches of river
- Largest nuggets deposited in coarse sediment and finer gold in sandy parts of the sediment.
- Can occur with heavy minerals such as magnetite
- Angular irregular shaped nuggets.
- Generally gold nuggets larger near the source and smaller further down the slope
- Often Specimen gold is found (Specimen gold still has the host rock attached.)
|Cause of Gold Deposit||
Caused by a change in velocity or direction of water flow, such as;
- Inside bends in the River
- Large boulders in the water flow
- Water slows down as it flows into a pool, estuary or lake
- Fissures, holes or natural traps in the stream
Moved by gravity or rockslides as the primary gold source erodes.|
Deposited due to a change of hill gradient such as;
- A depression in the hillside.
- Base of the hill prevents further movement
- Natural rock barrier prevents movement.
|Where to look for the Deposited Gold
The High Specific Gravity (SG) of gold means
it is transported at the base of currents and will be deposited by changes in currents.
So places to prospect for alluvial gold in stream or river beds are listed below.
The KEY is to imagine the stream in full flood then look for anywhere where there is a change in velocity or direction of the water;
- Find the direction of flow then prospect on and around the inside bend of the steam or river bank
- Gold will travel in the line of least resistance so look downstream to the next sharp inside bend and prospect in a straight line to that bend.
- Along that line look at the stream bed, is there obstructions such as hard rock dykes across the flow or boulders? If so look around those areas.
- If there are Fissures, holes or natural traps in the stream scrape out all the material in those natural traps.
- Check the overburden in all these stream traps right down to bedrock, then scrape out the fissures and holes in the bedrock.
- Even if the stream bedrock is bare granite or other igneous rock check it for fissures
- Look for holes, even those filled with cemented rubble and check these thoroughly down to bedrock.
- Coarse sediment and gravel deposits could hold larger gold nuggets, even if the deposit is not on the bedrock it could still contain small nuggets
- Not all the deposits are in current streams, try to identify where the streams flowed in the past and prospect there using these rules.
- Also remember that ancient river valleys and stream beds could have been covered by volcanic flows or uplifted by earth movement and be found on the tops or sides of hills.
- Detect on the edge and banks of salt lakes where streams flow into the lake from Gold Mining Areas.
- Look at low hills, rises and flats adjacent to gold producing areas such as old gold mines on hillsides. costeans or dryblowing sites.
- Prospect laterite profiles that have developed over bedrock.
- Look at the base of hills where there is ironstone and quartz rubble.
- Search on hillsides where there is a natural barrier such as a quartz vein or a Dyke.
- Follow the path down the hill from your gold find or the historical evidence and up the hill to try to find more nuggets or even the primary gold source.
- If there is a change of vegetation or grasses on the side of a hill check to see if there is deeper ground there where material has been deposited in a depression.
- Detect for coarse gold on the banks or edges of salt lakes at the bottom of slopes.
Dont forget to refer to the following pages to increase your understanding of;
How is Gold Formed.
Where to Find Gold.
Old Gold Mines.
Salt Lake Metal Detecting.
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