Also, zircons are magnetic so scientists can separate the finest pieces with magnets.
Once they isolated zircon samples, this is when the hard part begins. Geologists take one tenth of one percent of the rocks and examine them.
That way, scientists know the exact composition of that tiny sample.
A single grain of zircon may contain different compositions and ages. It is a difficult concept to wrap our heads around, and yet through a lot of very detailed work both in the field and in the laboratory, geologists have found a way to go back in time and see how the world was millions and even billions of years ago.
The half-life of the uranium series is 4.47 billion years, and the half-life of the actinium series is 710 million years.The older they get, the farther out along the curve they go. However, even though zircon is very strong, sometimes a geological event occurs that allows lead to escape.This makes the zircons go straight back to the starting point on the Concordia graph, off of their original line. As long as no other geological event occurs, the whole Discordia line moves along the Concordia line, pointing to the age of the geological event that caused the disturbance. This means that any lead found in zircon minerals was made by radioactive decay, after the formation of the mineral. Zircon also concentrates Uranium (You) and (although less so) Thorium (Th) and excludes lead (Pb), which means it has a very high You/Pb ratio.