Fool’s gold, or “pyrite”, fools fools who are looking for gold in all the wrong places. It has a brassy color that can appear yellow, but that’s where the similarities end. Part of the reason fool’s gold can fool an untrained eye is because it can be found near or in small deposits of gold. Those deposits also tend to have arsenic, which contributed to the “fool” being fooled.
Pyrite is made of iron and sulfur and tends to look more like yellow grey than the bright gold of gold. It can also spark when struck with steel, so figuring out which is which is surprisingly easy.
The word “pyrite” comes from the Greek word for “on fire”, “pyritēs”. Ancient Romans actually used this term for several types of stone that could spark when struck. It was described in Pliny the Elder’s Naturalis Historia, the original encyclopedia. For some reason, the name “pyrite” stuck to fool’s gold.
Pyrite has a long history of use as a source of ignition. Starting before ancient Roman to start fires, through to the 1600s in early firearms. It’s been used just as long as a source of iron sulfate, an old school method of treating anemia. To get the iron sulfate, a mound of pyrite was left outside to weather. The runoff was collected and boiled, leaving behind iron sulfate to be used much the same way iron supplements are today. This also became the preferred method of acquiring sulfuric acid, a vital ingredient for fertilizer.
Use of pyrite in jewelry became a popular during the Victorian era in marcasite jewelry, and it’s been growing in popularity ever since.
It wasn’t until the 20th century pyrite started getting used in electronics. Originally, it was used in crystal radios during near the start of the century, until vacuum tubes became the norm. Recently, it’s being used in batteries and has been proposed as a main component of solar panels.