Also known as Fools Gold this stone can make fire by striking it against flint. As this stone makes fire it's not such a hard leap to understand that it's believed to be able to help with lethargy as it gives energy, just like a fire is made up of energy.
It takes away listlessness replacing that with alertness and a feeling of alertness making you feel fresh again. It'll do this for mental tiredness as well as physical giving you endurance for working with your body. Mentally it'll help to improve memory, find ideas and express those ideas with intelligence.
It isn't surprising to find that for the body it is meant to increase the oxygen in the blood and is also beneficial to the lungs and we know that plenty of oxygen is needed for the brain to work well.
In history it has been discovered that it was used as an amulet by the ancient Mexicans and that their Shamans would use it to aid in meditation, they would carve one side of it with spiritual symbols and polish the other side of it to make a reflective mirror. This was one of the first stones to be used as a healing amulet kept in a Shaman's bag.