Rainbow colors on the ruby

[mastercut]

Hello,
I own a rather nice ruby that (as far as I know) is heat treated. I haven´t appraised it yet and will do soon, but I would like to ask anyway... The ruby shows a rainbow like appearance on some parts of its surface - like a petrol on the street in fact What could it mean?

 

[PrecisionGem]

It means that there is a fracture or other type of inclusion in the stone. This will give it that "oil slick" look.

 

[LD]

Has it got a lab report? What you're seeing could also be evidence of lead fissure filling. A GOOD appraiser and one used to identifying treatments may be able to tell you whether he/she thinks it's been filled but my preferred route (especially if the Ruby has a significant value to you) would be to get it checked by a reputable lab. Unfortunately treating rubies is fairly common place now with dying, filling etc etc. Fingers crossed yours is heat only.