Zircon

Zircon is a zirconium silicate mineral and is the main source of the metal zirconium. It is NOT cubic zirconia (a synthetic simulant). Zircon is a natural, spectacular gemstone that rivals diamond in brilliance and fire due to its high refractive index and dispersion. Zircon crystals from the Jack Hills in Australia are the oldest known solids on Earth, dated at 4.4 billion years old.

Formation & Geology

Zircon is a common accessory mineral in igneous rocks (granite, syenite) and metamorphic rocks. Because it is physically hard and chemically resistant, it survives weathering well and accumulates in sedimentary sands (placers). Blue zircon, popular in jewelry, is usually produced by heat-treating brown zircon.

Physical Characteristics

Zircon has very high birefringence (double refraction), meaning that facets on the back of the stone appear doubled when viewed through the front. It is also brittle and can show abrasion on facet edges (paper wear). It often contains trace radioactive elements (uranium, thorium) which can damage the crystal structure over eons (metamictization).

Historical Significance

In the Middle Ages, zircon was believed to induce sound sleep, drive away evil spirits, and promote riches, honor, and wisdom. The name likely comes from the Persian word 'zargun', meaning 'gold-hued'. It is a birthstone for December.