Zircon and Zirconology - The Study of Zircon

Most gemstones formed millions of years ago, but zircon is truly exceptional. The oldest known zircon crystals, discovered in Western Australia, date back over 4.4 billion years, making zircon one of the very first minerals on Earth.

Blue, Pink and Golden Zircon Gemstones

As our planet formed 4.56 billion years ago, zircon was among the earliest crystals to emerge as molten granite cooled. Although the ancient granitic rocks have long eroded away, zircon remains preserved as tiny, durable grains — an incredible archive of Earth’s earliest crust. Some zircon crystals even predate the formation of the moon, which happened around 4 billion years ago.

Zircon has fascinated scientists so much that it has inspired its own field of study known as zirconology. Zircon’s structure can trap trace amounts of uranium and thorium, which decay at known rates, allowing researchers to date the crystals accurately using radiometric methods. Isotope analysis of oxygen within zircon has revealed signs of water in Earth’s crust more than 4 billion years ago, reshaping our ideas about when life may have first emerged. If water was present so early, it is possible life began much sooner than previously thought - long before the first nucleated cells appeared about 1.5 billion years ago.

Beyond its geological significance, zircon is equally intriguing to gemologists. It is an unusually dense mineral — roughly 50% denser than diamond. For example, if a diamond weighs 1 carat, a zircon of similar size will weigh around 1.5 carats. Because of this density, zircon gemstones can appear smaller than their carat weight suggests, so careful measurements are important when purchasing.

Zircon also shows pronounced birefringence, meaning it has two different refractive indices. As light passes through a doubly refractive stone, it splits into two rays, each traveling on different paths. This causes a zircon to sometimes look slightly fuzzy or display doubled facets when viewed through its table, which is why skilled gem cutters must work carefully to control these optical effects.

In addition to its strong birefringence, zircon has a high refractive index (1.810–2.024), approaching that of diamond (2.417–2.419), and impressive dispersion, giving it exceptional brilliance. Before the invention of modern diamond simulants, white zircon was even used as a diamond substitute. Zircon should not be confused with cubic zirconia, which is a lab-created diamond simulant. Zircon, on the other hand, is the oldest naturally occurring mineral known on our planet - truly a gem every collector should consider.

For a complete introduction, see our Zircon Info page.

Also, learn more about the properties of Zircon Stone to complement your zirconology knowledge.