Refractive index of barium sulfate What is the refractive index of barium respectively where do I find it? I only find values for alpha, beta and x-ray radiation like on https://pubchem.ncbi.nlm.nih.gov/compound/barium_sulfate#section=Decomposition

I need it for all wavelengths or at least at 455 nm. Thank you in advance!
The index of refraction of $\ce{BaSO4}$ at 589 nm can be found in "Index of Refraction of Inorganic Crystals", in CRC Handbook of Chemistry and Physics, 90th Edition (CD-ROM Version 2010), David R. Lide, ed., CRC Press/Taylor and Francis, Boca Raton, FL.

Separate values are given for the indexes of the orthorhombic crystals:

$\begin{align}
n_x &amp;= 1.6362\\
n_y &amp;= 1.6374\\  
n_z &amp;= 1.6480
\end{align}$