  Quark matter which contains s-quarks in addition to u- and d- could be stable
or metastable. In this case, lumps made of this strange matter, called
strangelets, could occasionally hit the Earth. When travelling through the
atmosphere they would behave not dissimilar to usual high-velocity meteors with
only exception that, eventually, strangelets reach the surface. As these
encounters are expected to be extremely rare events, very large exposure is
needed for their observation. Fluorescence detectors utilized in large
ultra-high energy cosmic ray observatories, such as the Pierre Auger
observatory and the Telescope Array are well suited for a task of the detection
of these events. The flux limits that can be obtained with the Telescope Array
fluorescence detectors could be as low as $5\times
10^{-22}~cm^{-2}~s^{-1}~sr^{-1}$ which would improve by 1.5 orders of magnitude
the strongest present limits obtained from ancient mica crystals.
