  We report on the production of a pure sample of up to 3x10^5 optically
trapped molecules from a Fermi gas of 6Li atoms. The dimers are formed by
three-body recombination near a Feshbach resonance. For purification a
Stern-Gerlach selection technique is used that efficiently removes all trapped
atoms from the atom-molecule mixture. The behavior of the purified molecular
sample shows a striking dependence on the applied magnetic field. For very
weakly bound molecules near the Feshbach resonance, the gas exhibits a
remarkable stability with respect to collisional decay.
