We present a real-time observation study of lamellar patterns in thin-sample directional solidification of a near-eutectic In-In2Bi metallic alloy. The spacing range of stability is shown to extend from about 0.9 lambda(JH) to 2.2 lambda(JH), where lambda(JH) is the Jackson-Hunt minimum undercooling spacing, in agreement with what was observed earlier in transparent eutectics. We analyze the time evolution of non-uniform spacing distributions using a previously established semi-empirical ``spacing-diffusion'' law [Akamatsu et al., Metal. Mater. Trans. A 35 (2004) 1815]. We obtain a quantitative estimate of the Jackson-Hunt constants and other material parameters relevant to eutectic growth, among which lambda V-2(JH) = 48 +/- 7 mu m(3) s(-1) and D = 505 +/- 75 mu m(2) s(-1), where V is the solidification speed, and D is the solute diffusion coefficient in the liquid. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.