Fit #1— Cauchy from (n_D, V_D estimated from silicate family)
Cauchy approximation
Valid 0.38–0.78 µm
n
n = 1.5950VD = 60.0
n(λ)=1.58+0.005191/λ2
Na-Zr silicate. Dispersion estimated. n_D from published gemological tables; V_D estimated from silicate family because species-specific dispersion is not widely reported. Source: Winchell / GIA / Liddicoat compilations.