Spotting Synthetic and Treated Gemstones

## The Difference Between Synthetic and Treated These two categories are distinct and often confused. A **synthetic gemstone** has the same chemical composition and crystal structure as its natural counterpart but was grown in a laboratory rather than formed by geological processes. Synthetic ruby is corundum (Al2O3) with chromium impurities, chemically identical to natural ruby. Synthetic diamond is pure carbon in a cubic crystal structure, identical to natural diamond. A **treated natural gemstone** is a genuine stone from the earth that has been subjected to some process — heat, irradiation, chemical impregnation, fracture filling — to alter its appearance. Heat-treated sapphire was dug from the ground; humans just adjusted its color in a furnace. Both categories carry disclosure obligations. Neither is inherently fraudulent — the fraud occurs when they are sold as something they are not. ## Synthetic Gemstones: Production Methods and Telltale Signs ### Flame Fusion (Verneuil Process) Developed in 1902, this is the oldest and cheapest synthetic production method. Powdered materials fall through an oxygen-hydrogen flame and melt, building up a synthetic crystal called a "boule." Flame fusion rubies and sapphires have been sold commercially for over 100 years. Telltale signs: Curved growth lines (striae) visible under magnification — a consequence of the boule rotating during growth. Natural rubies and sapphires have angular growth zones, not curved ones. Flame fusion stones also often contain gas bubbles. ### Hydrothermal Growth Mimics how natural stones form in hydrothermal veins — superheated water dissolves and recrystallizes minerals onto a seed crystal under pressure. Hydrothermal emeralds (Chatham, Biron, Tairus brands) are more difficult to distinguish from natural than flame fusion products. Characteristic inclusions: Chevron-patterned growth zones, "nail-head" spicules (short, rod-like inclusions). Hydrothermal synthetic emeralds typically have higher water content, detectable by infrared spectroscopy. ### CVD and HPHT Diamonds Lab-grown diamonds are produced by two main methods: Chemical Vapor Deposition (CVD) and High Pressure High Temperature (HPHT). Both produce optically and chemically genuine diamonds. Detection requires specialized equipment — DiamondView, FTIR spectroscopy, or photoluminescence testing — that most jewelers do not possess. GIA and other labs have invested heavily in detection technology. Lab-grown diamonds of gem quality now sell at 50–85% discounts to natural diamonds, which has created a large secondary market. The FTC requires disclosure; reputable sellers comply. ## Common Gem Treatments ### Heat Treatment The most widespread treatment in the colored stone trade. Heat treatment improves color by dissolving or restructuring color-causing inclusions, and can improve clarity by dissolving silk (fine rutile needles) in sapphire. - **Sapphire**: Heating at 1600–1800°C dissolves silk inclusions, often dramatically improving clarity and color. Rutile needles that previously caused a star effect disappear. Unheated sapphires with good color command significant premiums. - **Ruby**: Heating at lower temperatures (around 900–1500°C) improves color and heals fractures partially. Beryllium diffusion — heating in the presence of beryllium — can dramatically change color and is a more controversial treatment. - **Tanzanite**: Virtually all tanzanite on the market has been heated. Rough tanzanite is brown-red; heating converts it to the blue-violet color for which it is known. - **Aquamarine**: Often heated to remove greenish hues, producing the pure blue color most valued. Detection: Disrupted or missing silk in sapphire, altered inclusion halos, and chemical analysis. Lab reports from GIA, Gübelin, and SSEF reliably detect and report heating evidence. ### Fracture Filling **Emerald oiling**: Emeralds almost universally contain fractures reaching the surface (their "jardin"). Filling these with colorless oil, cedar oil, or optically matched resins improves apparent clarity. Minor oiling with traditional oil is considered acceptable trade practice. Heavy filling with colored resins is not. Disclosure is required. Detection: Examination under ultraviolet light — certain fillers fluoresce. Infrared spectroscopy identifies filler type. GIA, AGL reports grade extent of filling as "none," "minor," "moderate," or "significant." **Ruby lead glass filling**: Highly fractured, low-quality ruby rough is impregnated with lead-glass or bismuth-glass filler, dramatically improving clarity of material that would otherwise be nearly opaque. These stones sell cheaply but are misrepresented as natural ruby. The filler can be dissolved by common cleaning agents including ultrasonic cleaners and even acids in perspiration with prolonged contact. Detection: Unusual luster in fractures (glass-like flash), gas bubbles in fractures under magnification, rapid acid testing. ### Irradiation Blue topaz — nearly all of it — is colorless or pale topaz irradiated to produce blue. Blue, yellow, pink, and "padparadscha" sapphires can be irradiated. Irradiation treatments in sapphire are unstable and may fade with light exposure. ### Beryllium Diffusion Used primarily in sapphire (and some rubies) since around 2000. Heating corundum in a beryllium-rich environment diffuses beryllium into the outer layer of the stone, dramatically changing color — turning pale sapphire vivid orange, or improving ruby color. The treatment is detectable only by laser ablation ICP-MS (a sophisticated chemical analysis), not standard gemological tools. All major labs test for this. ## Practical Steps for Buyers 1. **Buy with a certificate** from GIA, AGL, Gübelin, or SSEF for any significant purchase. These labs use spectroscopic equipment that is beyond the reach of most dealers and buyers. 2. **Examine under a loupe**: Curved striae indicate flame fusion synthetics. Gas bubbles in fractures indicate glass filling. A 10x loupe is a $30 investment that pays for itself. 3. **Ask the seller directly**: Legitimate sellers disclose treatments without hesitation. Evasion is information. 4. **Price check**: Prices far below market suggest the stone is not what it's claimed to be.