Blue color zoning observed in some of the unusual rubies; immersed in

Color zoning in sapphire. Typical color zones forming 60º angles corresponding to hexagonal prism faces. FoV 7 mm.

Understanding Common Corundum Treatments

Russian crystal-growth laboratories are now producing hydrothermal

PDF) Challenging Synthetic Rubies Examined in GIA's Bangkok and Hong Kong Laboratories

Jonathan Muyal's research works

Strong blue color zones were observed in many of the Jegdalek rubies.

PDF) Challenging Synthetic Rubies Examined in GIA's Bangkok and Hong Kong Laboratories

Ruby Round 0.80 Carat - Rare Gemstone Company

Green Beryllium-Diffused Sapphire – Gemma News Service

Color distribution

Ruby and sapphires ::: Gemology

14 Mineral Descriptions – Mineralogy

What's up with my sapphire ring? Is this normal discoloration? : r/Gemstones

Ruby Emerald Cut 3.08 Carat - Rare Gemstone Company

Cobalt-Doped Glass-Filled Sapphire • Gem Treatment