  Within a nonlinear chiral Lagrangian framework, the underlying mixings among
quark-antiquark, four-quark and glue components of $f_0(1500)$ and $f_0(1710)$
are studied in a global picture that includes all isosinglet scalar mesons
below 2 GeV. The quark components are introduced in the Lagrangian in terms of
two separate nonets (a quark-antiquark nonet and a four-quark nonet) which can
mix with each other and with a scalar glueball. The free parameters of the
Lagrangian are studied by a simultaneous fit to more than 20 experimental data
and constraints on the mass spectrum, decay widths, and decay ratios of the
isosinglet scalars below 2 GeV. Moreover, constraints on the mass spectrum and
decay widths of isodoublet and isovector scalars below 2 GeV as well as
pion-pion scattering amplitude are also taken into account. The insights gained
in this global picture, due to the complexities of the mixings as well as the
experimental uncertainties, are mainly qualitative but are relatively robust,
and reveal that the lowest scalar glueball hides between $f_0(1500)$ and
$f_0(1710)$, resulting in a considerable mixing with various quark components
of these two states. The overall current experimental and theoretical
uncertainties do not allow to pin down the exact glue components of isosinglet
states, nevertheless it is shown that the $f_0(1500)$ and $f_0(1710)$ have the
highest glue component. While this global study does not allow precision
predictions for each individual state, it provides useful "family" correlations
among the isosinglet states that are found insightful in probing the
substructure of all scalars, in general, and the isosinglets, in particular.
The overall estimate of the scalar glueball mass is found to be $1.58 \pm 0.18$
GeV.
