Amalthea is thought to be a fragment from the mantle of a Vesta-sized, 300–600 km diameter parent body that broke up around one billion years ago, with the other major remnant being 9 Metis. The spectrum of 113 Amalthea reveals the presence of the mineral Olivine, a relatively rarity in the asteroid belt.
^Cloutis, E. A. (March 1993), "Olivine-rich asteroids, pallasitic olivine and olivine-metal mixtures: Comparisons of reflectance spectra", Lunar and Planetary Institute, Twenty-fourth Lunar and Planetary Science Conference. Part 1: A-F: 317–318, Bibcode:1993LPI....24..317C.
^Burbine, T. H. et al. (July 2000), "The Nature of Olivine Asteroids", Meteoritics & Planetary Science35: A35, Bibcode:2000M&PSA..35R..35B.