Tourmaline

Dravite

Refractive Index: 1.6500
Abbe Number: 60.0
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

= 1.6500

V_{D}

= 60.0

n (λ) = 1.6337 + 0.005671/ λ^{2}

Mg-rich tourmaline. Slightly higher RI than elbaite. GIA dispersion 0.017. Source: GIA / Winchell / Liddicoat gemological tables.

Absorption Specimens

Kenya, Coast Province (Taita-Taveta District), Taita Hills

Mexico, Baja California State (Ensenada Municipality)

Tanzania, Arusha Region, Landanai