Pyrite Gemstone Beads from Rings & Things. Also known as fool's gold, pyrite beads offer a glittering option for gemstone jewelry components. This semiprecious gemstone caused a lot of disappointment in the mid-1800s! Often mistaken for gold in the US Gold Rush, pyrite is actually iron sulfide and has an opaque, shiny, metallic luster. The gemstone trade often mistakenly calls these semiprecious beads marcasite (while marcasite has the same chemical composition as pyrite, it crystallizes differently). Pyrite has been used for thousands of years in the Americas. Today, pyrite is used to foster intelligence, mental stability, logic, and analytical ability. It is said to open channels between the left and right brain. Be aware that pyrite can stain clothes as it oxidizes. With prolonged exposure to air and water, pyrite will begin to decompose into iron oxides and sulfate. For these reasons, it's best to store pyrite in a dry, airtight container when it's not being worn.