Zircon is a popular gemstone and the primary ore of zirconium, and comes in many colours. Unfairly confused with cubic zirconia (CZ) it has brilliant lustre and fire, combined with good hardness, making it a desirable gem. Zircon is actually the oldest known mineral on Earth. Considering that the Earth formed 4.56 billion years ago, the oldest zircon gemstones represent the earliest record of the Earth's crust. Read more about Zircon in our Gem Guide.