Frequently confused with the synthetic stimulant cubic zirconia, natural zircon is actually a magnificent, ancient gemstone and the oldest known mineral on Earth, with some crystals dating back over 4.4 billion years. Composed of zirconium silicate, it is celebrated for its incredible optical properties, boasting a high refractive index and intense dispersion—or “fire”—that allows it to split light into a dazzling rainbow of flashes that closely rivals a diamond. While colorless zircon was historically used as a brilliant diamond alternative, the gem occurs naturally in an earthy palette of warm reds, yellows, and browns, alongside highly coveted vibrant blue hues created through careful heat treatment. A defining characteristic of zircon is its strong double refraction; when looking through the table of a faceted stone, the pavilion facets appear doubled, giving the gem a uniquely rich, velvety depth and an undeniable, brilliant sparkle.