Rubies and sapphires are different colored varieties of the mineral corundum.
Are rubies rare.
Large gem quality rubies can be more valuable than comparably sized diamonds and are certainly rarer in fact smaller blue sapphires 1 3 cts are relatively abundant compared to small gem quality rubies.
In nature diamonds are rare but not so in the gem world.
Now corundum is a fairly common mineral.
The emery on your emery boards and sand paper may contain.
While rubies from thailand contain relatively high iron content which can result in overly dark reds with brownish or purplish overtones the geological conditions in myanmar generally produce rubies with very little trace iron.
They are also exceptionally scarce.
Ranking a 9 on the mohs scale of hardness diamond is a 10 corundum has been mined extensively for abrasives.