The metal aluminum is an element. Aluminum Oxide consists of 52.9% aluminum and 47.1% oxygen. Transparent alumina (NOT aluminum!) has existed forever. It's called corundum, the mineral that produces ruby and sapphire. A scientist named Verneuil developed a method called 'flame fusion' in the 1890s to make synthetic ruby and sapphire from powdered Al203.
This new process produces a 'glass' (not the same as silica glass) through a different procedure. The word "glass" is a generic term used to describe any substance, natural or man made, that exhibits certain properties. Melted borax produces a "glass" but it's not the same material as window or pop bottle glass.