Cordierite

Iolite

Refractive Index: 1.5356–1.5404
Abbe Number: 61.3–61.8
Crystal System: Isotropic (cubic)
Formation: Natural
Dispersion Data: Measured (published fit)
Fits: 2

Refraction Fits

Fit #1

Shannon / Cauchy

$n$

n

= 1.5404

V_{D}

= 61.3

n^{2} = 1 + \frac{λ ^{2}}{0.7501 ( λ ^{2} - 0.009999 )}

Fit #2— Specimen fit

Shannon / Cauchy

$n$

n

= 1.5356

V_{D}

= 61.8

n^{2} = 1 + \frac{λ ^{2}}{0.758 ( λ ^{2} - 0.009894 )}

Colorless

Absorption Specimens

Madagascar, Toliara Province (Bekily District), Beraketa

Myanmar, Mandalay Division, Mogok (Kyatpyin)

Sri Lanka, Sabaragamuwa Province, Ratnapura