  We have obtained the first beryllium measurements of late F/early G-type
stars in the old open cluster M67 (4.5 Gyr) and in the intermediate age cluster
IC 4651 (1.7 Gyr). One member of the young cluster IC 2391 (~50 Myr) was also
observed. Our sample stars have effective temperatures within a range of +30 -
+380 K from the solar temperature. All our sample stars, including the Sun and
the young cluster star have, within the errors, the same Be abundance. This
result implies that late F/early G-type stars undergo very little (if any) Be
depletion during their main-sequence life-time. Since these stars have
undergone some Li depletion, our finding is indicative of shallow mixing, i.e.
of a mixing process that can transport surface material deep enough for Li
burning to occur, but not deep enough for Be burning. As shown in previous
studies, the Li vs. Be diagram is a powerful diagnostic of stellar interiors.
In this context, we do not find any evidence of correlated Li and Be depletion;
furthermore, a comparison with various models shows that the Be pattern of our
sample stars is compatible only with models including gravity waves. This class
of models, however, cannot reproduce the Li observations of M 67.
