Iron pyrite (FeS2) is commonly known as “Fool’s Gold” because it resembles gold to the untrained eye. Pyrite has a brass-yellow color and metallic luster, but professionals can easily distinguish it from gold. Gold is very soft and will bend or dent easily, while pyrite is brittle and will break rather than bend. Gold leaves a yellow streak, while pyrite’s streak is greenish black.
Pyrite derives its name from the Greek word for fire (pyr) because it can create sparks for starting a fire when struck against metal or stone. This property made it useful for firearms at one time but this application is now obsolete. Pyrite was once a source of sulfur and sulfuric acid, but today most sulfur is obtained as a byproduct of natural gas and crude oil processing. Pyrite is still sometimes sold as a novelty item or costume jewelry.
But iron pyrite isn’t entirely useless; in fact it’s a good way to find real gold because the two form together under similar conditions. Gold can even occur as inclusions inside iron pyrite, sometimes in mineable quantities depending on how effectively the gold can be recovered.
Here’s another reason why “Fool’s Gold” isn’t so foolish. Several studies are underway to evaluate iron pyrite for photovoltaic applications, specifically solar cells for renewable energy.
A group of MIT researchers are studying the surface properties of pyrite to determine if pyrite could find significant use in solar cells. The researchers have found that the surface “energy bandgap,” of pyrite, a property essential for making solar cells or semiconductor devices, is less than half of the energy bandgap of the bulk material. Prior studies that evaluated the photovoltaic potential for pyrite were based on the bandgap of bulk material and produced poor results. The researchers suggest that solving the surface low bandgap issue could be the key to making pyrite work as a material for solar cells.
A University of California, Irvine team is taking another approach to developing iron pyrite for solar energy. Researchers are working on a technique to produce phase pure, colloidal pyrite nanocrystals on a large scale for use in thin film solar cells. The goal is to produce inexpensive, large-area modules by printing or spraying pyrite nanocrystal “solar paint” onto flexible metal foils. The design mimics existing technology and thus has the potential to be quickly commercialized.
Another study published on the National Center for Biotechnology Information web site discusses iron pyrite’s potential as semiconductor material for photovoltaics and as high energy density cathode material for batteries.The study suggests that issues with iron pyrite nanocrystal formation can be addressed by a new tactic based on a examining the nanostructure evolution and recrystallization to uncover how the shape, size and defects of iron pyrite nanocrystals changes during growth.
Should the issues with developing the full potential of iron pyrite be overcome, this mineral could prove a valuable energy resource. In the meantime, if you need to tell the difference between iron pyrite and real gold, know that XRF analyzers provide a fast, accurate, nondestructive method to determine the elemental composition of any sample. When testing precious metals, XRF quickly provides the exact karat weight and percentages of all elements within an item – easily identifying non-standard or counterfeit material. What’s more, some XRF instruments feature technology that can identify gold-plated items.
If you want to know more about how to tell real gold from “Fool’s Gold,” watch this video produced by the University of Knottingham.