In addition to our rational minds/knowledge we also have intuitive or otherworld knowledge.
In irish, book/reasoned knowledge is called sous and intuitive,otherworld knowledge is called fios.
Everytime we have a vision,voice,dream we are accessing fios knowledge,everybody has their intuition to guide them and as a source of knowledge.
I've had similar dreams,many people have prophetic dreams and they are called precognitive dreams which you can google.
Probably the stone is connected to your family history,past life or some other connection.
Or perhaps the universe just wanted you to know you are a psychic person who has the ability to access fios/otherworld knowledge.