  We numerically study the algebraic properties of the Weyl tensor through the
merger of two non-spinning black holes (BHs). We are particularly interested in
the conjecture that for such a vacuum spacetime, which is zeroth-order
algebraically general, a geometric horizon (GH), on which the spacetime is
algebraically special and which is identified by the vanishing of a complex
scalar invariant (${\mathcal{D}}$), characterizes a smooth foliation
independent surface (horizon) associated with the BH. In the first simulation
we investigate the level-$0$ sets of $\text{Re}({\mathcal{D}})$ (since
$\text{Im}({\mathcal{D}})= 0$) in the head-on collision of two unequal mass
BHs. In the second simulation we shall investigate the level-$\varepsilon$ sets
of $|{\mathcal{D}}|$ through a quasi-circular merger of two non-spinning, equal
mass BHs. The numerical results, as displayed in the figures presented, provide
evidence that a (unique) smooth GH can be identified throughout all stages of
the binary BH merger.
