Found Diamond

Thursday 7:18 pm est.
Good Evening!
I found what I believe to be a round diamond on a blacktop parking lot about 10 days ago. The gem is lose and when it caught my eye it appeared like an odd shaped metallic thing. I reached down to pick it up and see what it was and when I opened my hand, I was startled.
I have been afraid to take it in to have it viewed to determine it's authenticity, but I feel that I must. Someone has lost a very beautiful stone, regardless.
I have had a few friends look at it and they tell me it appears to be a diamond, it is heavy in weight and with my bare eyes, it looks perfect. I want to do the right thing, but I don't want to post it before I know it is the real deal.
Can you suggest ways for me to determine on my own if it's real and its possible value? I would also like to know if there is a way for me to see if it has a laser number inscribed on it?
I would appreciate your immediate consideration on answering my questions and getting back to me asap.
Thank you, Linda