As zircon becomes more and more modified by internal radiation damage, the density decreases, the crystal structure is compromised, and the color changes.
Zircon occurs in many colors, including reddish brown, yellow, green, blue, gray and colorless.
When an organism dies it ceases to replenish carbon in its tissues and the decay of carbon 14 to nitrogen 14 changes the ratio of carbon 12 to carbon 14.
Experts can compare the ratio of carbon 12 to carbon 14 in dead material to the ratio when the organism was alive to estimate the date of its death.
Zircon forms economic concentrations within heavy mineral sands ore deposits, within certain pegmatites, and within some rare alkaline volcanic rocks, for example the Toongi Trachyte, Dubbo, New South Wales Australia in association with the zirconium-hafnium minerals eudialyte and armstrongite.
Australia leads the world in zircon mining, producing 37% of the world total and accounting for 40% of world EDR (economic demonstrated resources) for the mineral.
In geological settings, the development of pink, red, and purple zircon occurs after hundreds of millions of years, if the crystal has sufficient trace elements to produce color centers.
Color in this red or pink series is annealed in geological conditions above temperatures of around 400°C.), one of the most refractory materials known.
If the amount of carbon 14 is halved every 5,730 years, it will not take very long to reach an amount that is too small to analyze.Because of their uranium and thorium content, some zircons undergo metamictization.Connected to internal radiation damage, these processes partially disrupt the crystal structure and partly explain the highly variable properties of zircon.Zircon has played an important role during the evolution of radiometric dating.Zircons contain trace amounts of uranium and thorium (from 10 ppm up to 1 wt%) and can be dated using several modern analytical techniques.
For example, hafnium is almost always present in quantities ranging from 1 to 4%.