So you've just received a delivery of some black limestone - whether that is a bunch of paving slabs, or a fireplace hearth - and upon inspection you spot a sparkle and see there are pieces of gold in the stone. What a discovery! 
You quickly want to know whether this gold may be worth something, which I assume is how you've ended up reading this.
Unfortunately I don't have good news for you. I'd love to tell you that you've found pure gold in your £400 pack of paving slabs and you will easily have made you your money back, but sadly this isn't the case. The mineral is likely Iron Pyrite as is commonly found in a lot of Limestone and is worth next to nothing - although it does add a nice shine and a unique signature to your stone.
How Iron Pyrite - or Fools Gold - Is Formed
Iron Pyrite is one of the most common 'sulfide' materials, so whilst it may look similar to gold, it's rarity is so low that it isn't worth anything at all!
Iron pyrite forms inside sedimentary rocks such as Black Limestone when there is a lack of oxygen and plenty of Iron and Sulphur in certain underground pockets. Decaying organic matter such as fossils, or waste remains consume the oxygen in the environments and release sulphur as they decompose. The sulphur then reacts with Iron to form this Iron Pyrite.
So What Is The Difference Between Fools Gold and Regular Gold?
As the video explains, there are many ways to tell fools gold apart from regular gold - so it's a good idea not to get ahead of yourself before deciding that you can retire on the new yacht you're planning to buy with your gold windfall.
Conclusion - Are You Rich? Probably Not
I can say with plenty of confidence that if you have a shiny vein in your new black limestone, there is very little chance this is gold - sadly 😢. The likelihood of whether this is gold or fools gold is dictated by where you found it, and finding the mineral inside layers of sedimentary rock means all signs point towards this gold looking stuff being fairly worthless Iron Pyrite, or 'fools gold'.
We apologies for any dreams shattered!
