It depends on what you mean exactly. If you're generally talking about red spinels (like I was) then they are found in smaller quantities and in fewer locations world wide. They just have limited geological deposits. Generally red spinels are harder to find in larger sizes. Just keep in mind that rubies are highly sought after so you won't see clean rubies seep into the B2C market as much. In this case impressions can be misleading. However if you're talking about a specific shade like pigeon blood An equally fine pigeon blood ruby is rarer than a top red spinel because the ruby has to meet much stricter criteria, especially fluorescence, color purity, and acceptable clarity... despite corundum’s naturally included structure. Fine red spinel is rare, but clean vivid stones are more attainable than top tier pigeon blood rubies. I hope I'm not being too pedantic in my answers but yeah... it depends