GIA G230: Synthetics, Simulants & Treatments Matrix

GIA G230 Diamonds & Diamond Grading

Synthetics, Simulants & Treatments

A rapid-reference diagnostic matrix designed for professional appraisers. Identify lab-grown signatures, recognize enhancement treatments, and separate common simulants in the field and at the bench.

Appraiser's Note

Always utilize proper magnification (10x loupe or microscope with darkfield illumination) when searching for these identifiers. When in doubt, advanced laboratory testing is required for definitive separation of natural vs. synthetic.

Diagnostic Matrix

Category	Subject	Key Microscopic / Optical Signatures	Lighting / Tools Needed
Lab-Grown	HPHT (High Pressure, High Temperature)	Metallic Flux Inclusions: Opaque, reflective, black or white metallic rods/flakes. May respond to a strong magnet. Color Zoning: Geometric, often cuboctahedral growth patterns (hourglass or cross shapes in fancy colors). Strain: Usually lacks the anomalous double refraction (strain) seen in natural diamonds.	Darkfield illumination, Magnets, UV Light (often fluoresces cross-shaped patterns).

	CVD (Chemical Vapor Deposition)	Pinpoint Clouds: Non-diamond carbon clustering along growth planes. Strain Patterns: Distinctive linear or "tatami" (cross-hatched) strain patterns. No Metallic Flux: CVD does not use metallic catalysts.	Cross-polarized filters (polariscope/microscope) for strain, Darkfield for pinpoints.

Treatments	Fracture Filling	Flash Effect: The primary diagnostic. Brilliant flashes of color changing based on lighting background (e.g., Orange/Purple or Pink/Blue). Trapped Bubbles: Flattened gas bubbles trapped within the filler material in the fracture. Crackled Texture: Older fillers may show a web-like, crackled appearance over time.	Darkfield & Brightfield illumination (rocking the stone gently to catch the flash).

	Laser Drilling	Drill Holes: Tiny, whitish, surface-reaching tubes extending inwards toward an inclusion. KM Drilling: (Kiduah Meyuhad) "Worm-like" irregular, stepped channels resulting from internal lasers causing fractures to reach the surface, mimicking natural feathers.	10x Loupe or Microscope (focusing deeply into the stone from the surface).

Simulants	Moissanite (Synthetic SiC)	Facet Doubling (DR): Due to high double refraction. Look through kite facets towards the pavilion; opposite facet junctions will appear doubled/blurry. Needle Inclusions: Long, parallel, whitish needles running parallel to the optic axis. Dispersion: Higher "fire" than natural diamond (can look overly colorful).	10x Loupe (viewing at an angle), Thermal/Electrical testers (can give false diamond readings on older thermal testers).

	Cubic Zirconia (CZ)	Optics: Singly refractive (no doubling). Extreme lack of inclusions (often "too perfect"). Wear & Tear: Lower hardness means abraded facet junctions, scratches, and a "rounded" look over time compared to diamond's sharp edges. Weight: Noticeably heavier (higher specific gravity) than a diamond of the exact same dimensions.	10x Loupe (checking for abrasions), Scale & Calipers (for estimated weight vs actual), Standard Thermal Tester.

Advanced Field Screening: Lab-Grown vs. Natural Diamonds

1. Girdle Inscriptions

Most lab-grown diamonds are legally required to carry a microscopic laser inscription on the outer edge (the girdle). Under a 10x jeweler's loupe, you will see a registry number alongside explicit text such as LABORATORY GROWN or LG.

2. Advanced Gemological Equipment

Professional jewelers and independent gem labs rely on specialized, high-tech devices to screen stones.

Type IIa Screening (Infrared Spectrometers)

Roughly 98% of natural diamonds contain trace amounts of nitrogen (Type Ia). Conversely, nearly all lab-grown diamonds are structurally engineered to be chemically pure carbon, classified as Type IIa. Screening tools check the stone's light absorption properties; if it flags as Type IIa, it is highly likely to be lab-grown and must be sent for further analysis.

Aura IQ Diamond Tester

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Photoluminescence and UV Imaging: Systems look at fluorescent graining patterns under varying wavelengths of UV light. Natural diamonds show millions of years of erratic growth, while lab stones glow under patterns tracing modern manufacturing (sharp layered growth of CVD or hourglass patterns of HPHT).

SmartPro MAX

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Dual Thermal & Optical Conductivity: Standard selectors only check if a stone is a diamond or a fake simulant (like CZ). Multi-probe testers utilize combined thermal and complex optical sensor checks to accurately read differing microscopic structures caused by a diamond's rapid growth acceleration in a lab.

3. Microscopic Inclusions Analysis

When viewed under high-powered gemological microscopes, the microscopic structural imperfections (inclusions) trapped inside the stone tell the true story of its geological or synthetic origin:

HPHT Growth Inclusions

Because HPHT diamonds are grown inside intense metallic molten flux solutions, they often trap microscopic specks of industrial metals (like iron, nickel, or cobalt). These look like tiny, dark metallic opaque shapes that do not exist in natural diamonds.

CVD Growth Inclusions

CVD diamonds are grown line-by-line via a carbon plasma gas cloud. Under specialized magnification, they can reveal distinct, perfectly linear parallel growth lines or unique dark carbon pinpoint clusters.

Natural Earth-Mined Inclusions

Earth-mined diamonds contain organic imperfections formed over billions of years, such as tiny trapped crystals of other natural minerals (like garnet), feathers, or cleavages that follow natural geological fault lines.

Field Appraisal Quick Tips

The Magnets Test

A strong neodymium magnet can sometimes attract HPHT synthetic diamonds due to the metallic flux remnants. If a mounted stone reacts to a magnet, proceed with extreme caution and recommend lab testing.

Finding the Flash

Fracture fillers have a different refractive index than diamond. To spot the flash effect, slowly rock the diamond back and forth under a focused light source. The color will suddenly "flash" as the angle changes.

The Tilt Test (Moissanite)

Moissanite is cut to hide its double refraction when viewed straight down through the table. You must tilt the stone and look through the crown/kite facets toward the culet to spot the facet edge doubling.

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