Cosmic ray strangelets

Searching for strangelets in cosmic rays may be the best way to test the possible stability of strange quark matter. I review calculations of the astrophysical strangelet flux in the GV–TV rigidity range, which will be investigated from the Alpha Magnetic Spectrometer (AMS-02) on the International Space Station, and discuss the merits of strangelets as ultra-high energy cosmic rays at EeV–ZeV energies, beyond the Greisen-Zatsepin-Kuzmin cutoff. I also address some ``counter-arguments’’ sometimes raised against the possibility of stable strangelets. It will be argued that stability of strange quark matter remains a viable possibility, which must be tested by experiments.