White Sapphire Dispersion (Corundum)

Physically-modeled COLOURLESS sapphire (corundum, Al2O3) dispersion, built from the real ordinary-ray Sellmeier equation of Malitson & Dodge, J. Opt. Soc. Am. 62, 1405 (1972): n_o^2 = 1 + 1.4313493lam^2/(lam^2-0.0726631^2) + 0.65054713lam^2/(lam^2-0.1193242^2) + 5.3414021*lam^2/(lam^2-18.028251^2), lam in um - not tuned by eye. At the sodium D line (589.3nm) this gives n=1.7681, matching the standard textbook value for sapphire (n_o=1.768) to four figures. Per-channel refractive indices used here: R 1.76603 @630nm, G 1.77170 @532nm, B 1.77765 @465nm. Computed F/C-line dispersion (n486nm-n656nm) is 0.0106 - about 0.43x this creator's own diamond asset and a small fraction of the moissanite asset's - the real, checkable reason a sapphire shows much less rainbow 'fire' than a diamond or moissanite of the same cut, not a claim taken on faith. IMPORTANT: this models colourless corundum ('white sapphire', a real traded gem variety) only. Blue sapphire and ruby get their colour from trace Cr3+/Fe2+/Ti4+ absorption, which this material does not simulate - tint the base colour yourself if you need a coloured stone. Real sapphire is weakly birefringent (no=1.768 vs ne~1.760); this material uses only the ordinary-ray index and does not model double refraction, the same simplification already disclosed on this creator's moissanite asset. Channel tint colors are the CIE 1931 color-matching function's actual response at each sampled wavelength. Uses the standard three-IOR additive-Glass-BSDF technique for Cycles/Eevee. Apply to any faceted gem-cut mesh - this asset ships the material only, not geometry. Same CIE 1931 code already shipped and tested in this creator's Caustify spectral path tracer and the N-BK7/N-SF11/diamond/moissanite materials.

A separate paid pack (all five materials — N-BK7, N-SF11, diamond, moissanite, sapphire — plus a ready-to-render Cycles demo scene and labeled dispersion close-ups for each) is on Gumroad: https://laterrr.gumroad.com/l/mnziiy. This BlenderKit version stays free and unchanged.