A spin 3/2 baryon made up three strange quarks (see strangeness). The existence of the omega-minus particle, as well as its properties, were predicted by Murray Gell-Mann in 1962 as part of a scheme to classify baryons, called the eightfold way. The omega-minus particle was subsequently discovered experimentally, thus demonstrating the validity of the eightfold way. This discovery was historically very important in the theoretical understanding of the strong interactions. The mass of the omega mass particle is 1672.5 MeV and its average lifetime is 0.8 × 10−10 s. The omega minus particle has an electric charge of −1 (its antiparticle has a charge of +1).
http://www.bnl.gov/bnlweb/history/Omega-minus.asp A bubble-chamber photograph of the discovery of the omega-minus particle