Famous Scottish Rock Hunting Sites: The Blue Hole

Made famous by the Scottish geology expert Professor Heddle, the exact location of the Blue Hole – an underground cavern which produced beautiful blue agates – is a mystery. Might you be the one to find it?

A nice example of a Scottish agate that features the blue-tinge coupled with onyx banding. One of our agates from 2022/23

Somewhere off the East Coast of Scotland there lies an underwater den of “blue” agate which has achieved legendary status thanks to its biggest fan Prof. Matthew Forster Heddle (1829-1897). Although we know sort of, kind of, almost, half-roughly where it is(?) we don’t really know where it is. All we know about the blue hole is that it produces fantastic blue-hued chalcedony in pretty patterns.

The Blue Hole is a bit of a rock hunting mystery here in Scotland. Renowned mineralogist and collector Prof. Heddle routinely collected rocks from around the locality he believed the hole to be, which is up in Angus. An estimated third of his collection of Scottish agates came from this treasure trove… but to this day the exact location remains uncertain. After all, a good Scottish rock hunter never reveals their exact sources.

But we can point you in kind of, sort of, almost, roughly – half of the right direction.

Another example of parralel lines in agate with that blue-tinge in clear chalcedony.

Searching for Heddle’s Blue Hole

Where to start? With what we know spelled out for us in one easy to understand article just like this one, courtesy of the Edinburgh Geological Society. Heddle was particularly interested in how the agates formed and so collected both nodules and fragments from the coast north of Edinburgh, north of St. Andrews, and south of Aberdeen.

His notes suggest that the famous blue hole was off the coast of the Usan/Lunan/Montrose area. All of these locations sport good agate hunting and would be worthy areas for a closer look. Don’t look at us either, we don’t know where it is. Although we have explored the area a few times, we really need a couple of weeks up there, studying the lay of the land. But the above article is a good starting point as it rightly explains that most agates in Scotland are in that central area of andesite and old lava flow.

Heddle speculated that the mossy edge to this type of agate came from suspended hornblende, mica, or other pegmatites.

Heddle made amazing contributions to what we know about agates today. Regardless of whether or not you find the hole, you should read his work for a deeper knowledge of Scottish agates. For example, his theory on how moss agates form due to flaking of zeolites or mica on vesicle walls will give you a new appreciation of how these stones form. They are not all formed in lava bubbles, after all.

The presence of an underwater cavern off the northeast coast of Scotland would explain the abundance of agates found in this region. However, we don’t know exactly where it is. Even the Mindat listing is exceptionally vague. At this stage, finding it is a matter of getting your boots wet and jumping in there.

Remember the rock hunting rules:

1.       Stay away from SSSI’s

2.       No mechanical stuff

3.       Protect our Shores

4.       Remove Rubbish as you hunt

5.       Don’t be smashing things with hammers, only loose material is ok.

And generally be thoughtful and appreciative of the land around you. We know we sure are.

Where to Start Rock Hunting for the Blue Hole

Well it is definitely somewhere south of Aberdeen and north of St. Andrews. In this region there are a number of towns who have burns and rivers leading to the sea, which might contain agates. Where would we look if we had the time and resources to find it? We would start with Lunan Bay, which we wrote about earlier in our Famous Scottish Crystal Hunting Locations series.

Asides from Lunan Bay, the Fishing Village of Usan and the town of Montrose are both mentioned in Heddle’s notes.

Arbroath

Agate Scotland have a great section on the Angus Coast which is worth a gander. And yes, they are absolutely correct, this place is rugged enough to kill you so please be careful.

If you want to walk the Angus coastline, Lunan Bay is a good place to begin although Arbroath does have it’s own agates. All you really need is to find a waterway or head north.

Montrose

Again, Montrose has its own agates set into the andesite bearing rocks. The little village of St Cyrus – which has an excellent hotel if you are travelling with your dog – has agates in the fields and waterways. Montrose itself is known for lovely pinks and greys, onyx and banding. Have a closer look at the Montrose agate gallery on Mindat here.

Usan

There are a number of small villages in this area where you can go for a walk and a rock hunt. Usan is little more than a handful of houses and a fishing outfit. There are fields in the middle of the town sort of thing. It’s a peaceful place. The shoreline is the same sort of black, exposed rock that you see for miles in all directions.

Remember to check the SSSI map before you go rock hunting and avoid protected areas. You can find it here courtesy of Nature Scot.

How Will You Know if You Find the Blue Hole?

That’s a great question. Presumably the presence of the hole will be signified by an abundance of specifically blue-hued agates. We advise that you be very careful not to fall in. It’s rugged coast, craggy cliffs, and jagged rocks the whole way. Stay safe out there.

And if you can’t be good? Be careful.