Fit #1— Cauchy from (n_D, V_D estimated from carbonate family)
Cauchy approximation
Valid 0.38–0.78 µm
n
n = 1.6250VD = 55.0
n(λ)=1.6079+0.005949/λ2
Na-Ca-Sr-REE carbonate. Dispersion estimated. n_D from published gemological tables; V_D estimated from carbonate family because species-specific dispersion is not widely reported. Source: Winchell / GIA / Liddicoat compilations.