G'day Martha and many thanks for your query
The origin (in a diamond mine?) sounds a little odd, so that is one of the reasons you are going to have to take it to a gemologist and have them test the item for you.
This is the only way you can PROVE it is what you think it is, and can stop guessing.
If it comes out of the ground then it must be natural.
If it's about the size of a lady bug (say one quarter of an inch or approx 6 millimeters) BUT THAT IS UNCUT!
By the time the cutter gets through with it, you might lose half of that in carat weight.
Currently a 6x4mm oval ruby weighs just over half of one carat – so it's not big – but remember I CAN'T SEE IT!
If you lose weight in the cutting – it would be a nice gem but a little on the small size – say one quarter of a carat.
Why not browse in your local FRIENDLY jewelry store window and look for something about that size, but don't take the price too seriously as they may have diamonds in the jewelry also.
My suggestion is get you gemologist (NOT YOUR JEWELER) to test it first.
Hope this helps and welcome to the Forum…