1 | What size of ruby do you have? | |
2 | This corundum type of gem is formed from a variety of aluminum oxide . | |
3 | This corundum type of gem is formed from a variety of aluminum oxide . | |
4 | True rubies are, in fact, the red variety of a mineral called corundum. | |
5 | In addition, there are some special species, such as abrasives, such as sintered corundum. |