Mardel, I am going to break the number one rule of gemology, never
sight identify a stone. I am very certain that the stone in your
ring is a synthetic corundum Alexanderite look alike, a flame fusion
corundum that has been doped to show some color change. These
stones are available as birth stones from most large stone and
jewelry suppliers. IE Trips and Rio Grande. Given the size of your
stone, and the description of it, it is almost certainly a
synthetic. These stones were very popular some years back, and were
sold as Alexanderites, with no mention of the synthetic origin.
You should however take the stone to a good jeweler/gemologist (not
a mall store salesman) and have them take a look. The number one
rule is there for a reason. You can never be sure without at least
three definitive observations. IE Ri, SG, Visual, UV, etc. and then
sometimes you are stumped.