The Verneuil flame-fusion process was invented to create artificial versions gemstones composed of this material.
The Verneuil flame-fusion process was invented to create artificial versions gemstones composed of this material. This and magnesium are found in spinel. Emery is mostly composed of this. Iron and titanium make this blue, while chromium makes it red. This is a nine on the Mohs scale. This is aluminum oxide. For 10 points, name this crystal that makes up rubies and sapphires.
The Verneuil flame-fusion process was invented to create artificial versions gemstones composed of this material.
{corundum} [or {aluminium} oxide before mentioned; or {ruby} before {spinel}]