  The isosinglet scalar mesons $f_0(1710)$, $f_0(1500)$, $f_0(1370)$ and their
mixing are studied. We employ two recent lattice results as the starting point;
one is the isovector scalar meson $a_0(1450)$ which displays an unusual
property of being nearly independent of quark mass for quark masses smaller
than that of the strange, and the other is the scalar glueball mass at 1710 MeV
in the quenched approximation. In the SU(3) symmetry limit, $f_0(1500)$ turns
out to be a pure SU(3) octet and is degenerate with $a_0(1450)$, while
$f_0(1370)$ is mainly an SU(3) singlet with a slight mixing with the scalar
glueball which is the primary component of $f_0(1710)$. These features remain
essentially unchanged even when SU(3) breaking is taken into account. We
discuss the sources of SU(3) breaking and their consequences on
flavor-dependent decays of these mesons. The observed enhancement of $\omega
f_0(1710)$ production over $\phi f_0(1710)$ in hadronic $J/\psi$ decays and the
copious $f_0(1710)$ production in radiative $J/\psi$ decays lend further
support to the prominent glueball nature of $f_0(1710)$.
