Herderite

Refractive Index: 1.6000
Abbe Number: 65.0
Crystal System: Isotropic (cubic)
Formation: Natural
Dispersion Data: Approximate (from n, V)
Fits: 1

Refraction Fits

Fit #1— Cauchy from (n_D, V_D)

Cauchy approximation

Valid 0.38–0.78 µm

$n$

n

= 1.6000

V_{D}

= 65.0

n (λ) = 1.5861 + 0.004832/ λ^{2}

Ca-Be fluorophosphate. GIA dispersion 0.017. Source: GIA / Winchell / Liddicoat gemological tables.

Absorption Specimens

Brazil, Minas Gerais State, Virgem da Lapa

Brazil, Minas Gerais State, Virgem da Lapa