The cavity ringdown technique has been employed for the spectroscopic characterization of the AuSi molecule, which is generated in a pulsed supersonic laser vaporization plasma reactor. Fifteen rovibronic bands have been measured between 340 nm-390 nm, 8 of which have been analyzed to yield molecular properties for the X and D (2) Sigma states of AuSi. This assignment is in disagreement with previous emission studies of AuSi, which had assigned the ground electronic state as a (2) Pi state. A time-of-flight mass spectrometer simultaneously monitors species produced in the molecular beam and has provided evidence for facile formation of polyatomic gold silicides. Comparison of AuSi with our recent results for CuSi and AgSi indicates regular bonding trends for the three coinage metal silicide diatoms.