Geology special! Finding gold…in Scotland

Naturally occurring gold is a bit like snakes, tornadoes and gun-crime. You kind of assume it just ‘doesn’t happen’ in the UK.

But it totally does! You just need to know where to look. The crown jewels are made of Welsh gold. And the crown of Scotland, which I didn’t even know existed until I posted this, is made of Scottish gold.

So let’s take a break from my usual data/technology/programming posts and go find some Scottish gold!

 

Where to look

There are several sites around Scotland where small deposits of gold occur naturally. I won’t go through the list, but I’ve left some links at the bottom which give more information.

One of the most famous deposits is near Helmsdale on the North East coast. This is relatively close to where I live in Aberdeen. There is a really nice campsite nearby at Crakaig Loth, so Hannah and I stayed there for the night and drove up to Helmsdale the next day. The Timespan museum rents out gold panning gear for £5, so we called in there first.

map

It looks close, but it’s still a 4 hour drive from Aberdeen

The actual gold-panning site, Kildonan Burn, is about 10Km to the West of Helmsdale. It is owned by the Suisgill estate who allow anyone to pan for gold in the burn. There are a few rules, but they are all perfectly reasonable. See the links at the bottom of the page for more information.

 

Where the gold comes from

In Scotland, gold was transported to the surface by hot volcanic water. Basically, the rock itself contained very low concentrations of gold. The hot, acidic water gradually dissolved small quantities. As it reached the surface, the gold precipitated out, becoming naturally concentrated.

Most gold in Scotland is found either in the Dalradian formation which extends to Northern Ireland (gold is also found in this formation there); or the Silurian formation in the Southern uplands.

The deposits near Helmsdale are a little different – they originate from a Cambrian volcanic intrusion. Interestingly, no one has ever found the source of the gold at Helmsdale. It has been found in the gravel in the local streams but no one knows where it actually originates from. Regardless, streams naturally concentrate gold as it is eroded from the nearby rock and settles at the river bed.

Another point of interest is the Beatrice oilfield. Found 11km offshore from Helmsdale. Much like the gold here, this was formed in an entirely different geological formation to the other oilfields in the North Sea.

 

How to pan for gold

I’ve been watching a lot of Cody’s lab recently. I strongly recommend checking out his videos – he is a geologist/generally smart guy who lives in the middle of Utah and gets up to all sorts of interesting experiments. His channel gave me the idea to do this in the first place.

My general philosophy was to go and have a nice day out. I wasn’t really expecting to find any gold, but I would be delighted even if I found a tiny trace of it.

After looking at a few Youtube videos, and reading a few guides, I felt like I had a pretty good idea of what to do:

 

Step one – find a good site

This is the key to actually finding something. There is no point panning gravel if there is no chance of it containing gold. Since gold is extremely dense, it is the first substance to ‘fall out’ of the stream and settle on the bed. This means looking for areas where the stream slows down. Behind large rocks,where the stream suddenly deepens, or under waterfalls are the best bet.

 

Step two – get digging

Since the gold tends to settle on the bedrock, we need to dig down to get there. The stream was pretty shallow, so there wasn’t much to dig through to get there. Obviously it was important to not just tear everything up – there is no point digging to the bedrock and clearing everything, including the gold, away. Once I had cleared most of the gravel, I sucked up the sediment from the bedrock with a gravel pump. I made this myself with a length of PVC pipe and a plunger made from a circle of MDF on a length of threaded bar.

IMG_0975

Using my gravel pump to suck up sediment from the river bed. Note, I am taking material from behind some large rocks where the flow naturally slows down.

I reckon a gravel pump is a necessity – you’d never be able to pick up gold directly from the bedrock without it.

 

Step three – into the pan

The gravel from the pump is then dropped into the pan through a griddle. This filters out the larger pebbles and just leaves gravel in the gold pan.

 

Step four – start panning

I found everything from this point really easy, and actually very therapeutic. First the pan is shook with plenty of water inside. This ‘fluidises’ the gravel and allows the denser material to sink to the bottom. If done correctly, any gold will end up sitting in the join between the base and wall of the pan.

IMG_0969

Look how excited I am!

Then it’s just a matter of washing off the lighter material from the top. This is done gradually and repeatedly, re-shaking the pan to keep everything graded.

IMG_0971

After most of the material is panned out.

When a couple of tablespoon’s-worth of material remain, we expect to see plenty of black sand. This consists of heavier iron-oxide/hematite which has settled at the bottom of the pan. Interestingly there didn’t seem to be much of that here. However, there were plenty of garnets left in the pan. I reckon there were at least 20 every time.

IMG_0972

This is typical of the heavier sediment left at the bottom of the pan.

 

Step five – gold!

Now it’s a case of gently swirling water past the remaining material. This gradually washes it away.

So, did I find anything? You bet I did. When there is gold in the pan, it is surprisingly obvious. Not only is it shiny, but it just sits there as everything else is washed around.

IMG_0964

Yeah, it’s not exactly a convincing photo

The glare in that photo doesn’t exactly help – let’s zoom in:

IMG_0964 (2)

It looks more obvious here, but it’s far easier to see in real life.

A teeny, tiny grain of gold! It took three attempts for me to find this. I had a pipette to transfer it into a vial. Of course, I lost the pipette within about 10 seconds of getting out of the car. So I had to carefully transfer it across with the tip of my penknife:

IMG_0973

Good job I’m used to soldering tiny components.

 

How much did I find?

I spent about two hours trying, going through about 15 ‘pans-worth’. Here’s what I got from those two hours of work:

IMG_0967

9 grains of gold – all smaller than 1mm. Let the good times roll!

About half of my attempts gave me a tiny grain or two of gold. Sure, it’s an absolutely tiny amount, but I’m absolutely delighted I managed to find anything at all. It just feels so weird to find gold in Scotland!

No post of mine would be complete without a bit of maths. Let’s do a completely ‘back of an envelope’ calculation to figure out the concentration of gold in the river sediment:

  • Each grain of gold is about 0.7X0.7X0.7mm = 0.343mm^3
  • That gives a mass of 0.008g per grain of gold I found.
  • I panned about 4kg of gravel (rough estimate) to get each grain.
  • So, the panned gravel contained 1 part gold per 500000.
  • By area, about 1/1000 of the stream was suitable for panning. And about 1/10 of the gravel from each site was near enough the bedrock to be panned.
  • So, I reckon about (1/500000)*(1/1000)*(1/10) of the gravel in the stream consists of gold.

This equates to 1 part in 5 billion*. And I separated it out with a bit of pipe, a sieve and a glorified bowl.

* remember, this is a rough estimate. A few larger nuggets would easily increase the concentration by an order of magnitude.

 

Links and further reading

https://www.youtube.com/user/theCodyReeder            Cody’s lab on youtube. This is where I got the idea from

http://pmg.leeds.ac.uk/pdfs/gold_poster.pdf                 A quick guide to gold in Scotland from Leeds university.

http://www.helmsdale.org/         The Helmsdale website. More info on the local area and where to hire the kit.

http://www.suisgill.co.uk/           The Suisgll estate. Where to pan for gold. This site also includes the rules for gold panners.

http://www.bgs.ac.uk/           For anyone wanting to get more technical. The British Geological Survey has an absolute wealth of information regarding gold in Scotland, England, Wales and Northern Ireland.

 

 

 

 

 

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s