The sapphire/ruby is a single crystal rhombohedral struture made of Aluminum Oxide (Al203).

Aluminum Oxide in its natural state is a very fine white powder.
The synthetic industrial sapphire/ruby is obtained from the controlled fusion of this very fine powder (Al203) in special ovens at a temperature of 2040 °C.

When heated to this temperature the powder melts and can then be formed into a single crystal of such extreme hardness ( 9 Mohs st ) that it is second only to diamond and which can be precision fabricated to meet all possible needs.

Several crystal growth methods exist, each having differing results in quality, size and costs.
The EFG or Stephanov methods allow for the growth of a crystal into a dictated shape ( for example ribbons ) but create limitations in the final usage.
By contrast using the Czochralski, HEM or Kiropolous methods you obtain a water clear carrot shaped (boule) which is completely workable.

This material has exactly the same chemical and physical properties as the best quality aluminum ceramics, for example in resistance to abrasion, corrosion and high temperature.
Whatsmore the single crystal structure allows for a very high grade of finish and exact precision fabrication even at the smallest dimensions.

The synthetic industrial ruby is made when this very same material is doped with a small concentrate of chromium (Cr), typically in the range of 0.05%, which produces shades of red without effecting the mechanical properties in any way.