- Visual observation: (10x lens) Look for color, luster, cut, doublet/triplet junctions, if any.
- Determine optic character: Single refractive (SR) / Double refractive (DR) / Anomalous Double refractive (ADR) / Aggregate (AGG).
- Spectrum: Many green stones may have diagnostic spectrum.
- Microscope: Inclusions may be diagnostic, but look for inclusions that differentiate natural and synthetic, doublet / triplet.
- Dichroscope: Different cutting orientations of natural and synthetic corundum / beryl may be revealed by dichroscope.
- Fluorescence: Look under shortwave and longwave for diagnostic colors.
- Immersion cell: Use immersion cell and high refractive index liquid to separate doublets/triplets.
- Refractometer: Confirm spectroscope reading with refractometer.
The green stones, which may resemble one another in appearance and values, are:
Fluorite
- Hardness: 4
- Specific gravity: 3.18
- Refractive index: 1.434
- Optic sign: SR
- Birefringence: -
- Other points: Inclusions, color, Chelsea color filter. Fluorite may be treated. Gem quality fluorites are relatively clean. Common look-alikes include emerald, tsavorite garent, peridot, demantoid garnet, green sapphire and glass. Standard / analytical techniques may be required to detect treatments / identify the stones.
Chalcedony (stained)
- Hardness: 6.5
- Specific gravity: 2.60
- Refractive index: 1.53 (mean)
- Optic sign: AGG (aggregate)
- Birefringence: -
- Other points: Color, stain, Chelsea color filter, inclusions. Chalcedony may be treated. Common look-alikes include jadeite jade, nephrite jade and glass. Standard identification techniques may be required to detect treatments.
Emerald
- Hardness: 7.5
- Specific gravity: 2.70 (average)
- Refractive index: 1.57 – 1.58
- Optic sign: Uniaxial negative
- Birefringence: DR; 0.006
- Other points: Color, inclusions, spectrum, fluorescence. To separate natural vs synthetic use microscope. Most emeralds are treated. Clean emeralds are difficult to find. Common look-alikes include fluorite, tsavorite garnet, demantoid garnet, peridot and glass. Standard / analytical techniques may be required to detect treatments / identify the stones.
Synthetic emerald
- Hardness: 7.5
- Specific gravity: 2.70 (average)
- Refractive index: 1.57 – 1.58
- Optic sign: Uniaxial negative
- Birefringence: DR; 0.003
- Other points: Color, inclusions, fluorescence, spectrum. Flux and hydrothermal stones may show diagnostic inclusions. Most gem quality stones are relatively clean. Standard / analytical techniques may be required to identify the stones if they are clean.
Tourmaline
- Hardness: 7
- Specific gravity: 3.05
- Refractive index: 1.62 – 1.64
- Optic sign: Uniaxial negative
- Birefringence: DR; 0.018
- Other points: Color, pleochroism, inclusions. Most tourmalines are treated. Gem quality stones are relatively clean. Common look-alikes include peridot, tsavorite garnet, chrome diopside, green sapphire, emerald and glass. Standard / analytical techniques may be required to detect treatments / identify the stones.
Jadeite jade
- Hardness: 7
- Specific gravity: 3.34
- Refractive index: 1.66 (mean)
- Optic sign: AGG (aggregate)
- Birefringence: -
- Other points: Color, inclusions, spectrum, Chelsea color filter. Most jadeite jades are treated. Common look-alikes include nephrite jade, chalcedony, serpentine, green zoisite, soapstone, idocrase, aventurine quartz and glass. Standard / analytical techniques may be required to detect treatments.
Peridot
- Hardness: 6.5
- Specific gravity: 3.34
- Refractive index: 1.65 – 1.69
- Optic sign: Biaxial positive
- Birefringence: DR; 0.037
- Other points: Color, inclusions, spectrum, birefringence, doubling of back facets. Common look-alikes include tourmaline, chrome diopside, tsavorite garnet, demantoid garnet, green sapphire and glass. Standard identification techniques may be required to identify the stones.
Enstatite
- Hardness: 5.5
- Specific gravity: 3.20 – 3.00
- Refractive index: 1.65 – 1.68
- Optic sign: Biaxial positive
- Birefringence: DR; 0.010
- Other points: Color, inclusions, spectrum. Enstatite may look like peridot. Standard identification techniques may be required to identify the stones.
Diopside
- Hardness: 5
- Specific gravity: 3.30
- Refractive index: 1.67 – 1.70
- Optic sign: Biaxial positive
- Birefringence: DR; 0.025
- Other points: Color, inclusions, doubling of back facets. Common look-alikes include tourmaline, tsavorite garnet, demantoid garnet, peridot, green sapphire and glass. Gem quality stones are relatively clean. Standard identification techniques may be required to identify the stones.
Green zoisite
- Hardness: 6.5
- Specific gravity: 3.35
- Refractive index: 1.69 – 1.70
- Optic sign: Biaxial positive
- Birefringence: DR; 0.009
- Other points: Color, pleochroism, inclusions. Green zoisite may be treated. Gem quality stones are relatively clean and may look like alexandrite. Translucent to opaque quality stones may look like jadeite jade, aventurine quartz or glass. Standard / analytical techniques may be required to detect treatments / identify the stones.
Tsavorite garnet
- Hardness: 7.25
- Specific gravity: 3.65
- Refractive index: 1.75
- Optic sign: SR
- Birefringence: -
- Other points: Color, inclusions. Common look-alikes include chrome diopside, green tourmaline, green sapphire, demantoid garnet, peridot, emerald and glass. The stones may be treated. Gem quality stones are relatively clean. Standard / analytical techniques may be required to identify the stones.
Demantoid garnet
- Hardness: 6.5
- Specific gravity: 3.85
- Refractive index: 1.89
- Optic sign: SR
- Birefringence: -
- Other points: Color, inclusions, spectrum, dispersion, negative refractive index. Common look-alikes include tsavorite garnet, green tourmaline, chrome diopside, green sapphire, peridot, emerald and glass. The stones may be treated. Standard / analytical techniques may be required to detect treatments / identify the stones.
Chrysoberyl
- Hardness: 8.5
- Specific gravity: 3.72
- Refractive index: 1.74 – 1.75
- Optic sign: Biaxial positive
- Birefringence: DR; 0.009
- Other points: Color, inclusions, spectrum. Common look-alikes include green sapphire, tsavorite garnet, demantoid garnet, peridot, tourmaline, fluorite and glass. The stones may be treated. Standard / analytical techniques may be required to detect treatments / identify the stones.
Green sapphire
- Hardness: 9
- Specific gravity: 4
- Refractive index: 1.76 – 1.77
- Optic sign: Uniaxial negative
- Birefringence: DR; 0.008
- Other points: Color, inclusions, spectrum. Common look-alikes include tsavorite garnet, demantoid garnet, green zircon, peridot, chrome diopside, green tourmaline and glass. The stones may be treated. Standard / analytical techniques may be required to identify treatments / identify the stones.
Green zircon
- Hardness: 6.5
- Specific gravity: 4
- Refractive index: 1.82 (values are variable)
- Optic sign: Uniaxial positive
- Birefringence: DR; 0.01
- Other points: Color, inclusions, negative refractive index, doubling of back facets, spectrum. Common look-a likes include green sapphire, peridot, chrome diopside, peridot, chrysoberyl, tsavorite garnet, demantoid garnet, emerald and glass. The stones may be treated. Standard / analytical techniques may be required to detect treatments / identify the stones.
Synthetic cubic zirconia
- Hardness: 8.5
- Specific gravity: 5.65 +
- Refractive index: 2.15 +
- Optic sign: SR
- Birefringence: -
- Other points: Color, negative refractive index reading, luster, dispersion. Standard / analytical techniques may be required to identify the stones.
Diamond
- Hardness: 10
- Specific gravity: 3.52
- Refractive index: 2.42
- Optic sign: SR/ADR
- Birefringence: -
- Other points: Rare; color, negative refractive index reading, luster, dispersion, spectrum, inclusions. Green diamonds may be treated. Analytical techniques may be required to detect treatments.
Syntheic green diamond
- Hardness: 10
- Specific gravity: 3.52
- Refractive index: 2.42
- Optic sign: SR/ADR
- Birefringence: -
- Other points: Color, negative refractive index reading, luster, dispersion, spectrum, inclusions. Synthetic diamonds are produced by high pressure high temperature method. Gem quality stones are relatively clean. Analytical techniques may be required to identify the stones.
Glass
- Hardness: 5.5
- Specific gravity: 3.70
- Refractive index: 1.60 – 1.66
- Optic sign: SR
- Birefringence: -
- Other points: Color, soft, inclusions (gas bubbles, swirls), luster. Standard identification techniques may be required to identify the stones.
Assembled Stones
Doublets / Triplets
Beryl composites
Refractive index: 1.57 -1.59
Birefringence: DR; 0.004
Other points: Immersion (Look for differences in color and luster between the sections)
Quartz soude (quartz/quartz)
- Refractive index: 1.54 -1.59
- Optic sign: Uniaxial positive
- Birefringence: DR; 0.009
- Other points: Look for differences in color and luster between the sections, gas bubbles)
Synthetic spinel soude (spinel / spinel)
- Refractive index: 1.728
- Optic sign: SR/ADR
- Birefringence: -
- Other points: Look for differences in color and luster between the sections, gas bubbles)
Garnet topped doublet (glass)
- Refractive index: 1.76 +
- Optic sign: SR/ADR
- Birefringence: -
- Other points: Look for differences in color and luster between the sections, gas bubbles)
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