The refractive indices of Sc2W3O12, measured at wavelengths of 435.8-643.8 nm, were used to calculate n(a) = 1.7331, n(b) = 1.7510, n(c) = 1.7586 at lambda = 589.3 nm and n(infinity) values at lambda = infinity from a one-term Sellmeier equation. Mean refractive indices, < n(D)>, and mean dispersion values, < A >, are, respectively, 1.7475 and 110 x 10(-16) m(2). Total electronic polarizabilities, alpha(obs), were calculated from n(infinity) and the Lorenz-Lorentz equation. The unusually large difference between the observed polarizability of 28.415 angstrom(3) and the calculated total polarizability alpha(T) of 26.74 angstrom(3) (Delta = +6.3%) is attributed to (1) a large M-O-W angle, and (2) a high degree of W 5d-O 2p and Sc nd-O 2p hybridization, where n signifies unspecified Sc d orbitals. (C) 2011 Elsevier Ltd. All rights reserved.