Zircon is a zirconium silicate mineral abundant in the Earth’s crust that produces rare crystal specimens that can be found in a variety of colors. It is also the primary ore of the metal zirconium and a popular gemstone that has been mined for over 2000 years. Its color variety is due to specific elemental impurities, of which some can be radioactive. Blue is the most often sold gemstone color of zircon. Colorless zircon has a brilliance and fire that rivals diamonds and for this reason, zircon can be viewed as a valuable diamond simulant. Its tetragonal crystal system can form short, stubby, small prismatic crystals with occasional double termination. Zircon is very resistant to chemical and mechanical weathering and very stable at high temperatures thus is a mineral that plays an important role in industrial products as a refractory material. Its durable chemical makeup has allowed zircon to survive ages of major geologic events. Zircon is the oldest mineral on Earth, dating back to more than 4.4 billion years ago. Scientists are able to get this number using a method called radiometric dating from radioactive zircon samples that contain uranium or thorium present within their structure formed at the time of crystallization. Zircon’s occasional trace amounts of radioactivity can undergo a process called metamiction to stabilize, although this destroys its crystalline structure. While heat treatment is a common practice for this mineral to undergo in order to enhance transparency and color, it is best to avoid prolonged sunlight and ultraviolet exposure with gem-grade zircon. Industrial zircon is mined from land and marine-based deposits of alluvial origin in Australia, South Africa, China, Indonesia, Madagascar, Sri Lanka, Kenya, Ukraine, Sri Lanka, and Brazil. Gem grade zircon has historically been found in alluvial deposits, within pegmatites, carbonate igneous rocks known as carbonatites, and in limestones altered by hydrothermal metamorphism found in Sri Lanka, Germany, Russia, USA, Cambodia, Myanmar, Vietnam, Nigeria, Australia, and Madagascar. Zircon crystals of high clarity at least several millimeters in size are suitable for use as gemstones and are rare.
