Fool's Gold is another name for Iron Pyrite, or more accurately, Iron Disulfide.
It is comprised of one Iron molecule and two Sulphur molecules. It has often been called Fool's Gold because the minerals metallic appearance and the fact that it invariably appears under the same conditions as gold has often caused it to be mistaken for the precious metal, gold.
The image shows an example of the single mineral you will receive. It will not be the exact mineral in the photo, the contents size, colour, shape and style may vary as with any natural item.
(20p not included - only shown to give an idea on size of the mineral).