When you see or feel teeth below, it's too long. Since it is wiggling, it's already ready to come out. Sometimes the tooth is ready but it won't fall out on it's own easily anyway. I had to take my son to the dentist once because he was so afraid of pulling it off that it re-anchored but a new tooth was coming out. My kids usually took max a week but eventually they get used to it and pull it out in a day or two.
Source: Unknown. Iron ore was first discovered by European settlers when the early land surveyor, William Austin Burt, was shown iron ore by an Indian chieftain near what is now Negaunee, Michigan, in 1844. He had noticed a strange movement of his compass needle while surveying near where the present town of Ishpeming is located.
Short answer: the Iron Age began when humans learned how to extract iron from the ground and make it into tools and weapons. Not an event. More like a gathering of knowledge and skill over many years.