  The mineral tetrahedrite Cu$_{12}$Sb$_{4}$S$_{13}$ exhibits a first-order
metal--insulator transition (MIT) at $T_{\rm MI}$ = 85 K and ambient pressure.
We measured the $^{63}$Cu-NMR at ambient pressure and the resistivity and
magnetic susceptibility at high pressures. $^{63}$Cu-NMR results indicate a
nonmagnetic insulating ground state in this compound. The MIT is monotonically
suppressed by pressure and disappears at $\sim1.0$ GPa. Two other anomalies are
observed in the resistivity measurements, and the pressure -- temperature phase
diagram of Cu$_{12}$Sb$_{4}$S$_{13}$ is constructed.
