Framboids are dominantly made of pyrite. The limiting factors for other minerals forming framboids include the requirements of crystal habit, solubility, and natural abundances of the constituent elements for framboid formation. Detailed examination of reports of non-pyritic framboids reveal microcrystalline material within and associated with framboids (e.g., greigite) and sub-spherical crystalline aggregates (e.g., marcasite, chalcocite-digenite, magnetite). Framboids are sometimes observed replaced by other minerals. Pyrite framboids are often formed during the earliest stages of sedimentation or mineralization and therefore are subject to further reactions with later fluids. Minerals such as copper, cobalt, zinc, and lead sulfides often display framboidal forms that have replaced original pyrite framboids. Likewise, oxidation of pyrite under some conditions can produce iron (oxyhydr)oxide and iron sulfate framboids.