I agree with everyone above; that being said, do your homework with the synthetics and get through it. One of the main tricks with corundum cutting is the final polish, which is usually the difference between good and superior. I use BATT laps charged with 3000 grit diamond and 100,000 grit diamond. I use WD40 to clean and charge them. If you can envision your engagement ring with multiple 3 or 4 mm natural untreated rubies rather than a ten million dollar stone contact me privately. This type of rough is very difficult to acquire as it requires going to where it is mined and buying a parcel of it at the hole that it comes from (you will also need a master gemstone dealer from the country that you are in), rather than buying it from someone in a some town that is just trying to sell you something and then smuggling it out without paying the export duty on the material. You definitely need the master dealer to certify and validate your parcel and get the export certificates. If you are that far into it, you will find that most items are exported as “samples” and pay only a 6% duty on something that is called samples or roughly 20 dollars. Far easier than getting caught at the airport and spending time in a Tanzanian prison. The fine to get you out would be roughly the retail value of the rubies.