Question about a silver ring with a stone

Hello! My question is is it possible to have a diamond on a silver ring? I own this silver ring with a baguette cut stone. Ring is marked J*A 925. On the diamond tester set to three or four, it fills the scale one square before the end! (I have a lot of jewelry with stones including gold, but no other stone does this)! I guess even and if it's a diamond it's synthetic...?! How do I determine how much it costs?

 

Diamonds are sometimes set in silver, but your stone is not a diamond.
At 9 on the Mohs scale it could be a sapphire (leucosapphire), either natural or synthetic. But it is best to have it tested.

 

I have tested the stone with Diamond selector 2, it determines the thermal conductivity of the stone! Basically, the instructions say that any crossing of the border and entry into the red sector, regardless of the squares, only happens when a diamond is present! If anyone knows how far to put the selector in the test - please help, the stone is approximately 8 x 4 mm in size.

 

Do you have a diamond in a different piece of jewelry? What I do with those testers is test something I know for sure is a diamond, get a positive result in the tester and turn the selector down to a point just where it tests positive. Do a 2nd test, be sure the genuine diamond is testing, then test the piece in question.