Emerald gemstone

I have opened a box of old stones that I have collected over the years, I came across a guy years ago who had what I described as gold fever, he would buy gold from anyone as long as it was cheap and had no interest in the stones, unless they was diamond, he had been at it for 20 years, sold me a load of filthy dirty stones that I then cleaned. It was great fun seeing all the shapes and colours of the stones. I am sure a few might be really good, but as usual I ain’t done nothing with them yet.
I knew I had this one, and It seems like it could be Columbia emerald, which is the only stone I can find that looks like it. It weighs 3.70 ct & I have seen small stones selling for big money. Is it possible I could have some major finds. Are stones so rare nowadays that they are changing hands for crazy money.