It is a common misconception in the gemstone trade to confuse Zircon with the synthetic material “Cubic Zirconia.” From a mineralogical standpoint, they are entirely unrelated. Zircon is a natural zirconium silicate ($ZrSiO_4$) and is the oldest mineral on Earth, with some crystals dating back over 4.4 billion years.
Because of its high refractive index and double refraction, it is one of the few gemstones that can technically compete with a diamond in terms of “brilliance” and “fire.”
1. Chemical Composition and Atomic Structure Zircon belongs to the nesosilicate group. Its structure consists of isolated silica tetrahedra ($SiO_4$) linked by zirconium cations ($Zr^{4+}$).
Density: Zircon is remarkably dense. It has a high Specific Gravity (around 4.7), meaning a one-carat zircon will appear smaller than a one-carat diamond or sapphire. Metamictization: This is a unique technical aspect of zircon. Over millions of years, trace amounts of radioactive elements (Uranium and Thorium) within the crystal can break down the internal lattice.
High Zircon: Crystals with a fully intact lattice (high luster and brilliance). Low Zircon: Crystals where the lattice has been damaged by radiation, resulting in a “cloudy” or greenish appearance and lower physical properties.
2. Optical Properties: Luster and Fire Zircon is prized in the industry for its Optical Dispersion—the ability to split white light into the colors of the rainbow.
Refractive Index (RI): Zircon’s RI ranges from 1.810 to 1.984. For context, this is significantly higher than sapphire or beryl, giving the stone an “Adamantine” (diamond-like) luster. Birefringence (Double Refraction): Zircon is strongly double-refractive. When looking through the table of a faceted zircon, you can often see “facet-doubling”—where the back facets appear as two lines instead of one. This adds a unique depth and “fullness” to the stone’s appearance.
3. Commercial Varieties and Colors While Zircon is found in many colors at the “Mouth of the Mine,” the trade categorizes them as follows: Blue Zircon: The most popular commercial variety. Most blue zircon is produced by heat-treating brownish crystals found in Southeast Asia and parts of Africa.
Red and Orange (Hyacinth): Naturally occurring vivid reds, oranges, and brownish-reds. These are often found in East African deposits.
Green Zircon: Rare and typically “Low Zircon” (metamict). Collectors prize these for their mossy, mysterious appearance. Colorless (Matura Diamond): Because of its fire, colorless zircon was historically used as a natural alternative to diamonds.
4. Mining and East African Production Zircon is a rugged mineral. It is highly resistant to chemical erosion, which is why it survives in river gravels (alluvial deposits) long after its host rock has washed away.
For your company’s vertical integration, East Africa (specifically Tanzania and Madagascar) has become a critical source for “earth-toned” zircons—golds, rose-pinks, and deep honey-oranges. These stones are increasingly popular because they are often “untreated,” appearing exactly as they did when they were extracted.
5. Physical and Technical Specifications Property Technical Value Chemical Formula $ZrSiO_4$ Mohs Hardness 6.5 – 7.5 Crystal System Tetragonal Refractive Index 1.810 – 1.984 Specific Gravity 3.90 – 4.73 Fracture Conchoidal to Uneven (Brittle)
6. Practical Considerations for the Buyer While Zircon is hard (7.5), it is notoriously brittle. In the trade, we talk about “paper wear”—where the edges of the facets can chip if stones are rubbed together in a parcel.
Setting: It is best suited for pendants, earrings, or protective ring settings. Identification: The “facet doubling” mentioned earlier is the easiest way for a professional to distinguish a natural Zircon from a Diamond or a synthetic substitute at a glance.
