Agate vs Amazonite — how do you tell them apart?	Optic character differs: AGG (Agate) vs DR (biaxial −) (Amazonite); RI 1.530–1.543 vs 1.514–1.530, SG 2.58–2.64 vs 2.54–2.58
Agate vs Amber — how do you tell them apart?	Agate is AGG, Amber is SR — polariscope separates; RI 1.530–1.543 vs 1.539–1.545, SG 2.58–2.64 vs 1.05–1.09
Agate vs Amethyst — how do you tell them apart?	RI separates: 1.530–1.543 (Agate) vs 1.544–1.553 (Amethyst); SG 2.58–2.64 vs 2.63–2.65
Agate vs Ametrine — how do you tell them apart?	RI separates: 1.530–1.543 (Agate) vs 1.544–1.553 (Ametrine); SG 2.58–2.64 vs 2.63–2.67
Agate vs Aventurine — how do you tell them apart?	RI separates: 1.530–1.543 (Agate) vs 1.544–1.553 (Aventurine); SG 2.58–2.64 vs 2.64–2.69
Agate vs Carnelian — how do you tell them apart?	RI 1.530–1.543 (Agate) vs 1.530–1.543 (Carnelian); SG 2.58–2.64 vs 2.58–2.64. Inclusions and spectroscope may be needed
Agate vs Chalcedony — how do you tell them apart?	RI 1.530–1.543 (Chalcedony) vs 1.530–1.543 (Agate); SG 2.58–2.64 vs 2.58–2.64. Inclusions and spectroscope may be needed
Agate vs Chrysocolla — how do you tell them apart?	SG separates: 2.00–2.40 (Chrysocolla) vs 2.58–2.64 (Agate); RI 1.460–1.630 vs 1.530–1.543
Alexandrite vs Color-Change Sapphire — how do you tell them apart?	Color-change sapphire: RI 1.762–1.770, SG 3.99–4.01, uniaxial negative; Alexandrite: RI 1.746–1.755, SG 3.70–3.78, biaxial positive. Optic character and SG separate
Alexandrite vs Diaspore — how do you tell them apart?	Diaspore: RI 1.685–1.752, SG 3.30–3.39, biaxial positive; Alexandrite: RI 1.746–1.755, SG 3.70–3.78, biaxial positive. SG cleanly separates (3.39 max vs 3.70 min)
Alexandrite vs Color-Change Garnet — how do you tell them apart?	Color-change garnet: SR, RI 1.740–1.765, SG 3.65–3.80; Alexandrite: DR (biaxial +), RI 1.746–1.755, SG 3.70–3.78. Polariscope separates — garnet shows single refraction
Alexandrite vs Synthetic Color-Change Corundum — how do you tell them apart?	Synthetic color-change corundum: RI 1.762–1.770, SG 3.97–4.05, uniaxial negative; Alexandrite: RI 1.746–1.755, SG 3.70–3.78, biaxial positive. Common simulant — RI and optic character separate
Alexandrite vs Almandine Garnet — how do you tell them apart?	Alexandrite is DR (biaxial +), Almandine Garnet is SR — polariscope separates; RI 1.746–1.755 vs 1.770–1.830, SG 3.70–3.78 vs 3.93–4.30
Alexandrite vs Cat's Eye Chrysoberyl — how do you tell them apart?	RI 1.746–1.755 (Alexandrite) vs 1.746–1.755 (Cat's Eye Chrysoberyl); SG 3.70–3.78 vs 3.70–3.78. Inclusions and spectroscope may be needed
Alexandrite vs Chrome Diopside — how do you tell them apart?	SG separates: 3.22–3.38 (Chrome Diopside) vs 3.70–3.78 (Alexandrite); RI 1.664–1.730 vs 1.746–1.755
Alexandrite vs Chrysoberyl — how do you tell them apart?	RI 1.746–1.755 (Chrysoberyl) vs 1.746–1.755 (Alexandrite); SG 3.70–3.78 vs 3.70–3.78. Inclusions and spectroscope may be needed
Almandine Garnet vs Pyrope Garnet — how do you tell them apart?	Both SR garnets; pyrope RI 1.730–1.760 vs almandine RI 1.770–1.830. SG: pyrope 3.62–3.87 vs almandine 3.93–4.30. SG and RI separate at extremes but blend in pyrope-almandine series
Almandine Garnet vs Rhodolite Garnet — how do you tell them apart?	Both SR garnets; rhodolite RI 1.740–1.770 vs almandine 1.770–1.830. SG: rhodolite 3.74–3.94 vs almandine 3.93–4.30. Lighter purplish-red hue in rhodolite
Almandine Garnet vs Cat's Eye Chrysoberyl — how do you tell them apart?	Almandine Garnet is SR, Cat's Eye Chrysoberyl is DR (biaxial +) — polariscope separates; RI 1.770–1.830 vs 1.746–1.755, SG 3.93–4.30 vs 3.70–3.78
Almandine Garnet vs Chrysoberyl — how do you tell them apart?	Almandine Garnet is SR, Chrysoberyl is DR (biaxial +) — polariscope separates; RI 1.770–1.830 vs 1.746–1.755, SG 3.93–4.30 vs 3.70–3.78
Almandine Garnet vs Color-Change Garnet — how do you tell them apart?	SG separates: 3.93–4.30 (Almandine Garnet) vs 3.65–3.80 (Color-Change Garnet); RI 1.770–1.830 vs 1.740–1.765
Almandine Garnet vs Color-Change Sapphire — how do you tell them apart?	Color-Change Sapphire is DR (uniaxial −), Almandine Garnet is SR — polariscope separates; RI 1.762–1.770 vs 1.770–1.830, SG 3.99–4.01 vs 3.93–4.30
Almandine Garnet vs Diaspore — how do you tell them apart?	Diaspore is DR (biaxial +), Almandine Garnet is SR — polariscope separates; RI 1.685–1.752 vs 1.770–1.830, SG 3.30–3.39 vs 3.93–4.30
Amazonite vs Turquoise — how do you tell them apart?	Amazonite (feldspar): RI 1.514–1.530, SG 2.54–2.58, DR, grid pattern; Turquoise: RI 1.610–1.650, SG 2.60–2.90, AGG. RI clearly separates
Amazonite vs Amber — how do you tell them apart?	Amazonite is DR (biaxial −), Amber is SR — polariscope separates; RI 1.514–1.530 vs 1.539–1.545, SG 2.54–2.58 vs 1.05–1.09
Amazonite vs Amethyst — how do you tell them apart?	SG separates: 2.54–2.58 (Amazonite) vs 2.63–2.65 (Amethyst); RI 1.514–1.530 vs 1.544–1.553
Amazonite vs Aventurine — how do you tell them apart?	SG separates: 2.54–2.58 (Amazonite) vs 2.64–2.69 (Aventurine); RI 1.514–1.530 vs 1.544–1.553
Amazonite vs Bloodstone — how do you tell them apart?	Optic character differs: DR (biaxial −) (Amazonite) vs AGG (Bloodstone); RI 1.514–1.530 vs 1.530–1.543, SG 2.54–2.58 vs 2.58–2.64
Amazonite vs Chalcedony — how do you tell them apart?	Optic character differs: AGG (Chalcedony) vs DR (biaxial −) (Amazonite); RI 1.530–1.543 vs 1.514–1.530, SG 2.58–2.64 vs 2.54–2.58
Amazonite vs Chrysocolla — how do you tell them apart?	SG separates: 2.00–2.40 (Chrysocolla) vs 2.54–2.58 (Amazonite); RI 1.460–1.630 vs 1.514–1.530
Amber vs Amethyst — how do you tell them apart?	Amber is SR, Amethyst is DR (uniaxial +) — polariscope separates; RI 1.539–1.545 vs 1.544–1.553, SG 1.05–1.09 vs 2.63–2.65
Amber vs Ametrine — how do you tell them apart?	Amber is SR, Ametrine is DR (uniaxial +) — polariscope separates; RI 1.539–1.545 vs 1.544–1.553, SG 1.05–1.09 vs 2.63–2.67
Amber vs Aventurine — how do you tell them apart?	Amber is SR, Aventurine is AGG — polariscope separates; RI 1.539–1.545 vs 1.544–1.553, SG 1.05–1.09 vs 2.64–2.69
Amber vs Bloodstone — how do you tell them apart?	Amber is SR, Bloodstone is AGG — polariscope separates; RI 1.539–1.545 vs 1.530–1.543, SG 1.05–1.09 vs 2.58–2.64
Amber vs Carnelian — how do you tell them apart?	Carnelian is AGG, Amber is SR — polariscope separates; RI 1.530–1.543 vs 1.539–1.545, SG 2.58–2.64 vs 1.05–1.09
Amber vs Chalcedony — how do you tell them apart?	Chalcedony is AGG, Amber is SR — polariscope separates; RI 1.530–1.543 vs 1.539–1.545, SG 2.58–2.64 vs 1.05–1.09
Amethyst vs Iolite — how do you tell them apart?	Both violet-blue; iolite: RI 1.535–1.547, SG 2.57–2.66, biaxial −, strong trichroism (violet/yellow/blue); Amethyst: RI 1.544–1.553, SG 2.63–2.65, uniaxial +, weak dichroism. Trichroism is diagnostic
Amethyst vs Charoite — how do you tell them apart?	Amethyst: RI 1.544–1.553, SG 2.63–2.65, uniaxial +, transparent; Charoite: RI 1.550–1.559, SG 2.54–2.68, AGG, translucent with swirling purple patterns. Texture is diagnostic
Amethyst vs Ametrine — how do you tell them apart?	Same species (quartz); ametrine shows bicolor purple/yellow zoning. Properties identical; visual zoning is diagnostic
Amethyst vs Scapolite — how do you tell them apart?	Scapolite: RI 1.540–1.572, SG 2.50–2.74, uniaxial −; Amethyst: RI 1.544–1.553, SG 2.63–2.65, uniaxial +. Optic sign separates; scapolite often shows cat's eye effect
Amethyst vs Aquamarine — how do you tell them apart?	SG separates: 2.68–2.78 (Aquamarine) vs 2.63–2.65 (Amethyst); RI 1.577–1.583 vs 1.544–1.553
Ametrine vs Aventurine — how do you tell them apart?	Optic character differs: DR (uniaxial +) (Ametrine) vs AGG (Aventurine); RI 1.544–1.553 vs 1.544–1.553, SG 2.63–2.67 vs 2.64–2.69
Ametrine vs Carnelian — how do you tell them apart?	RI separates: 1.544–1.553 (Ametrine) vs 1.530–1.543 (Carnelian); SG 2.63–2.67 vs 2.58–2.64
Ametrine vs Charoite — how do you tell them apart?	Optic character differs: DR (uniaxial +) (Ametrine) vs AGG (Charoite); RI 1.544–1.553 vs 1.550–1.559, SG 2.63–2.67 vs 2.54–2.68
Ametrine vs Iolite — how do you tell them apart?	Optic character differs: DR (biaxial −) (Iolite) vs DR (uniaxial +) (Ametrine); RI 1.535–1.547 vs 1.544–1.553, SG 2.57–2.66 vs 2.63–2.67
Ametrine vs Ivory — how do you tell them apart?	SG separates: 1.70–1.98 (Ivory) vs 2.63–2.67 (Ametrine); RI 1.535–1.540 vs 1.544–1.553
Andalusite vs Kornerupine — how do you tell them apart?	Both green/brown, biaxial; kornerupine RI 1.660–1.699, SG 3.27–3.45; Andalusite RI 1.629–1.649, SG 3.13–3.21. SG and RI separate; andalusite shows distinctive pleochroism (green/red/yellow)
Andalusite vs Apatite — how do you tell them apart?	Optic character differs: DR (biaxial −) (Andalusite) vs DR (uniaxial −) (Apatite); RI 1.629–1.649 vs 1.628–1.649, SG 3.13–3.21 vs 3.17–3.23
Andalusite vs Chrome Diopside — how do you tell them apart?	SG separates: 3.13–3.21 (Andalusite) vs 3.22–3.38 (Chrome Diopside); RI 1.629–1.649 vs 1.664–1.730
Andalusite vs Chrome Tourmaline — how do you tell them apart?	Optic character differs: DR (biaxial −) (Andalusite) vs DR (uniaxial −) (Chrome Tourmaline); RI 1.629–1.649 vs 1.624–1.660, SG 3.13–3.21 vs 3.00–3.20
Andalusite vs Clinohumite — how do you tell them apart?	Optic character differs: DR (biaxial −) (Andalusite) vs DR (biaxial +) (Clinohumite); RI 1.629–1.649 vs 1.625–1.675, SG 3.13–3.21 vs 3.13–3.35
Andalusite vs Chrysocolla — how do you tell them apart?	SG separates: 3.13–3.21 (Andalusite) vs 2.00–2.40 (Chrysocolla); RI 1.629–1.649 vs 1.460–1.630
Andalusite vs Danburite — how do you tell them apart?	SG separates: 2.97–3.02 (Danburite) vs 3.13–3.21 (Andalusite); RI 1.627–1.636 vs 1.629–1.649
Andalusite vs Enstatite — how do you tell them apart?	RI separates: 1.663–1.673 (Enstatite) vs 1.629–1.649 (Andalusite); SG 3.20–3.30 vs 3.13–3.21
Apatite vs Paraiba Tourmaline — how do you tell them apart?	Apatite: RI 1.628–1.649, SG 3.17–3.23, uniaxial −; Paraíba tourmaline: RI 1.624–1.644, SG 3.02–3.10. SG separates (apatite heavier); apatite is much softer (Mohs 5)
Apatite vs Chrome Diopside — how do you tell them apart?	RI separates: 1.628–1.649 (Apatite) vs 1.664–1.730 (Chrome Diopside); SG 3.17–3.23 vs 3.22–3.38
Apatite vs Chrome Tourmaline — how do you tell them apart?	RI 1.628–1.649 (Apatite) vs 1.624–1.660 (Chrome Tourmaline); SG 3.17–3.23 vs 3.00–3.20. Inclusions and spectroscope may be needed
Apatite vs Clinohumite — how do you tell them apart?	Optic character differs: DR (uniaxial −) (Apatite) vs DR (biaxial +) (Clinohumite); RI 1.628–1.649 vs 1.625–1.675, SG 3.17–3.23 vs 3.13–3.35
Apatite vs Chrysocolla — how do you tell them apart?	SG separates: 3.17–3.23 (Apatite) vs 2.00–2.40 (Chrysocolla); RI 1.628–1.649 vs 1.460–1.630
Apatite vs Coral — how do you tell them apart?	SG separates: 2.60–2.70 (Coral) vs 3.17–3.23 (Apatite); RI 1.486–1.658 vs 1.628–1.649
Apatite vs Danburite — how do you tell them apart?	SG separates: 2.97–3.02 (Danburite) vs 3.17–3.23 (Apatite); RI 1.627–1.636 vs 1.628–1.649
Aquamarine vs Topaz — how do you tell them apart?	Aquamarine (beryl): RI 1.577–1.583, SG 2.68–2.78, no cleavage; Blue topaz: RI 1.619–1.627, SG 3.49–3.57, perfect basal cleavage. SG clearly separates
Aquamarine vs Blue Diamond — how do you tell them apart?	Blue diamond: RI 2.417, SG 3.50–3.53, SR, extreme dispersion; Aquamarine: RI 1.577–1.583, SG 2.68–2.78. RI and dispersion immediately separate
Aquamarine vs Goshenite — how do you tell them apart?	Same species (beryl); aquamarine is blue/blue-green from Fe, goshenite is colorless. Properties overlap; color is the differentiator
Aquamarine vs Emerald — how do you tell them apart?	Same species (beryl); emerald colored by Cr/V (green), aquamarine by Fe (blue). RI: emerald 1.565–1.602 vs aquamarine 1.577–1.583. Spectroscope and Chelsea filter separate
Aquamarine vs Aventurine — how do you tell them apart?	RI separates: 1.577–1.583 (Aquamarine) vs 1.544–1.553 (Aventurine); SG 2.68–2.78 vs 2.64–2.69
Aquamarine vs Coral — how do you tell them apart?	Optic character differs: AGG (Coral) vs DR (uniaxial −) (Aquamarine); RI 1.486–1.658 vs 1.577–1.583, SG 2.60–2.70 vs 2.68–2.78
Aquamarine vs Grandidierite — how do you tell them apart?	SG separates: 2.85–2.98 (Grandidierite) vs 2.68–2.78 (Aquamarine); RI 1.590–1.623 vs 1.577–1.583
Aventurine vs Bloodstone — how do you tell them apart?	RI separates: 1.530–1.543 (Bloodstone) vs 1.544–1.553 (Aventurine); SG 2.58–2.64 vs 2.64–2.69
Aventurine vs Carnelian — how do you tell them apart?	RI separates: 1.530–1.543 (Carnelian) vs 1.544–1.553 (Aventurine); SG 2.58–2.64 vs 2.64–2.69
Aventurine vs Chalcedony — how do you tell them apart?	RI separates: 1.530–1.543 (Chalcedony) vs 1.544–1.553 (Aventurine); SG 2.58–2.64 vs 2.64–2.69
Benitoite vs Sapphire — how do you tell them apart?	Benitoite: RI 1.757–1.804, SG 3.64–3.68, uniaxial positive, strong dispersion; Sapphire: RI 1.762–1.770, SG 3.95–4.03, uniaxial negative. SG and optic sign separate
Benitoite vs Color-Change Garnet — how do you tell them apart?	Benitoite is DR (uniaxial +), Color-Change Garnet is SR — polariscope separates; RI 1.757–1.804 vs 1.740–1.765, SG 3.64–3.68 vs 3.65–3.80
Benitoite vs Color-Change Sapphire — how do you tell them apart?	SG separates: 3.64–3.68 (Benitoite) vs 3.99–4.01 (Color-Change Sapphire); RI 1.757–1.804 vs 1.762–1.770
Benitoite vs Kyanite — how do you tell them apart?	RI separates: 1.757–1.804 (Benitoite) vs 1.712–1.734 (Kyanite); SG 3.64–3.68 vs 3.53–3.68
Benitoite vs Spinel — how do you tell them apart?	Benitoite is DR (uniaxial +), Spinel is SR — polariscope separates; RI 1.757–1.804 vs 1.712–1.736, SG 3.64–3.68 vs 3.57–3.63
Benitoite vs Star Sapphire — how do you tell them apart?	SG separates: 3.64–3.68 (Benitoite) vs 3.95–4.03 (Star Sapphire); RI 1.757–1.804 vs 1.762–1.770
Benitoite vs Synthetic Color-Change Corundum — how do you tell them apart?	SG separates: 3.97–4.05 (Synthetic Color-Change Corundum) vs 3.64–3.68 (Benitoite); RI 1.762–1.770 vs 1.757–1.804
Benitoite vs Synthetic Spinel — how do you tell them apart?	Synthetic Spinel is SR, Benitoite is DR (uniaxial +) — polariscope separates; RI 1.725–1.728 vs 1.757–1.804, SG 3.52–3.65 vs 3.64–3.68
Black Opal vs Opal — how do you tell them apart?	Same species; black opal has dark body tone enhancing play of color. Both show play-of-color phenomenon. Body tone distinguishes
Black Opal vs Coral — how do you tell them apart?	Black Opal is SR, Coral is AGG — polariscope separates; RI 1.440–1.460 vs 1.486–1.658, SG 2.09–2.16 vs 2.60–2.70
Black Opal vs Obsidian — how do you tell them apart?	SG separates: 2.09–2.16 (Black Opal) vs 2.30–2.60 (Obsidian); RI 1.440–1.460 vs 1.480–1.510
Black Spinel vs Onyx — how do you tell them apart?	Black spinel: RI 1.712–1.730, SG 3.58–3.61, SR; Onyx: RI 1.530–1.543, SG 2.58–2.64, AGG. RI and SG clearly separate
Black Spinel vs Hematite — how do you tell them apart?	Hematite: RI 2.940–3.220, SG 4.95–5.30, very heavy, red streak; Black spinel: RI 1.712–1.730, SG 3.58–3.61. SG and streak test separate
Black Spinel vs Star Diopside — how do you tell them apart?	Star diopside: DR (biaxial −), RI 1.664–1.721, SG 3.27–3.36, shows 4-rayed star; Black spinel: SR, RI 1.712–1.730, SG 3.58–3.61. Polariscope, asterism, and SG separate
Black Spinel vs Jadeite — how do you tell them apart?	Black Spinel is SR, Jadeite is AGG — polariscope separates; RI 1.712–1.730 vs 1.654–1.688, SG 3.58–3.61 vs 3.24–3.43
Black Spinel vs Pearl — how do you tell them apart?	Black Spinel is SR, Pearl is AGG — polariscope separates; RI 1.712–1.730 vs 1.520–1.690, SG 3.58–3.61 vs 2.60–2.85
Black Spinel vs Rhodonite — how do you tell them apart?	Black Spinel is SR, Rhodonite is DR (biaxial +) — polariscope separates; RI 1.712–1.730 vs 1.716–1.752, SG 3.58–3.61 vs 3.57–3.76
Bloodstone vs Chrysocolla — how do you tell them apart?	SG separates: 2.58–2.64 (Bloodstone) vs 2.00–2.40 (Chrysocolla); RI 1.530–1.543 vs 1.460–1.630
Bloodstone vs Chrysoprase — how do you tell them apart?	RI 1.530–1.543 (Bloodstone) vs 1.530–1.543 (Chrysoprase); SG 2.58–2.64 vs 2.58–2.64. Inclusions and spectroscope may be needed
Bloodstone vs Emerald — how do you tell them apart?	SG separates: 2.58–2.64 (Bloodstone) vs 2.67–2.78 (Emerald); RI 1.530–1.543 vs 1.565–1.602
Bloodstone vs Moldavite — how do you tell them apart?	Moldavite is SR, Bloodstone is AGG — polariscope separates; RI 1.480–1.510 vs 1.530–1.543, SG 2.32–2.38 vs 2.58–2.64
Bloodstone vs Obsidian — how do you tell them apart?	Obsidian is SR, Bloodstone is AGG — polariscope separates; RI 1.480–1.510 vs 1.530–1.543, SG 2.30–2.60 vs 2.58–2.64
Blue Diamond vs Diamond — how do you tell them apart?	RI 2.417 (Blue Diamond) vs 2.417 (Diamond); SG 3.50–3.53 vs 3.50–3.53. Inclusions and spectroscope may be needed
Brown Diamond vs Smoky Quartz — how do you tell them apart?	Brown diamond: RI 2.417, SG 3.51–3.53, SR; Smoky quartz: RI 1.544–1.553, SG 2.63–2.65, DR (uniaxial +). RI and SG immediately separate
Brown Diamond vs Diamond — how do you tell them apart?	RI 2.417 (Brown Diamond) vs 2.417 (Diamond); SG 3.51–3.53 vs 3.50–3.53. Inclusions and spectroscope may be needed
Brown Diamond vs Sphalerite — how do you tell them apart?	SG separates: 3.51–3.53 (Brown Diamond) vs 3.90–4.10 (Sphalerite); RI 2.417 vs 2.369–2.500
Carnelian vs Fire Opal — how do you tell them apart?	Carnelian (chalcedony): RI 1.530–1.543, SG 2.58–2.64, AGG; Fire opal: RI 1.370–1.470, SG 1.98–2.20, SR. RI and SG clearly separate
Carnelian vs Citrine — how do you tell them apart?	RI separates: 1.530–1.543 (Carnelian) vs 1.544–1.553 (Citrine); SG 2.58–2.64 vs 2.63–2.65
Carnelian vs Ivory — how do you tell them apart?	SG separates: 1.70–1.98 (Ivory) vs 2.58–2.64 (Carnelian); RI 1.535–1.540 vs 1.530–1.543
Carnelian vs Red Beryl — how do you tell them apart?	SG separates: 2.66–2.70 (Red Beryl) vs 2.58–2.64 (Carnelian); RI 1.564–1.574 vs 1.530–1.543
Cassiterite vs Sphene — how do you tell them apart?	SG separates: 6.80–7.10 (Cassiterite) vs 3.45–3.55 (Sphene); RI 2.010–2.100 vs 1.843–2.110
Cassiterite vs Zircon — how do you tell them apart?	SG separates: 6.80–7.10 (Cassiterite) vs 4.60–4.80 (Zircon); RI 2.010–2.100 vs 1.925–1.984
Cat's Eye Chrysoberyl vs Chrysoberyl — how do you tell them apart?	Same species — cat's eye shows chatoyancy (single band of light from parallel needle inclusions). Standard gemological properties identical
Cat's Eye Chrysoberyl vs Color-Change Garnet — how do you tell them apart?	Cat's Eye Chrysoberyl is DR (biaxial +), Color-Change Garnet is SR — polariscope separates; RI 1.746–1.755 vs 1.740–1.765, SG 3.70–3.78 vs 3.65–3.80
Cat's Eye Chrysoberyl vs Diaspore — how do you tell them apart?	SG separates: 3.70–3.78 (Cat's Eye Chrysoberyl) vs 3.30–3.39 (Diaspore); RI 1.746–1.755 vs 1.685–1.752
Cat's Eye Chrysoberyl vs Grossular Garnet — how do you tell them apart?	Grossular Garnet is SR, Cat's Eye Chrysoberyl is DR (biaxial +) — polariscope separates; RI 1.734–1.759 vs 1.746–1.755, SG 3.57–3.73 vs 3.70–3.78
Cat's Eye Chrysoberyl vs Hessonite Garnet — how do you tell them apart?	Hessonite Garnet is SR, Cat's Eye Chrysoberyl is DR (biaxial +) — polariscope separates; RI 1.730–1.760 vs 1.746–1.755, SG 3.59–3.65 vs 3.70–3.78
Chalcedony vs Chrysocolla — how do you tell them apart?	SG separates: 2.58–2.64 (Chalcedony) vs 2.00–2.40 (Chrysocolla); RI 1.530–1.543 vs 1.460–1.630
Chalcedony vs Hauyne — how do you tell them apart?	Hauyne is SR, Chalcedony is AGG — polariscope separates; RI 1.494–1.509 vs 1.530–1.543, SG 2.44–2.50 vs 2.58–2.64
Chalcedony vs Ivory — how do you tell them apart?	SG separates: 1.70–1.98 (Ivory) vs 2.58–2.64 (Chalcedony); RI 1.535–1.540 vs 1.530–1.543
Chalcedony vs Rainbow Moonstone — how do you tell them apart?	SG separates: 2.68–2.72 (Rainbow Moonstone) vs 2.58–2.64 (Chalcedony); RI 1.559–1.572 vs 1.530–1.543
Charoite vs Iolite — how do you tell them apart?	RI separates: 1.550–1.559 (Charoite) vs 1.535–1.547 (Iolite); SG 2.54–2.68 vs 2.57–2.66
Charoite vs Scapolite — how do you tell them apart?	Optic character differs: AGG (Charoite) vs DR (uniaxial −) (Scapolite); RI 1.550–1.559 vs 1.540–1.572, SG 2.54–2.68 vs 2.50–2.74
Chrome Diopside vs Tsavorite Garnet — how do you tell them apart?	SG separates: 3.59–3.65 (tsavorite) vs 3.22–3.38 (chrome diopside); tsavorite is SR, chrome diopside is DR (biaxial −). Polariscope is diagnostic
Chrome Diopside vs Peridot — how do you tell them apart?	Both DR biaxial; chrome diopside RI 1.664–1.730 vs peridot 1.654–1.690. SG: chrome diopside 3.22–3.38 vs peridot 3.27–3.48. Peridot shows strong facet doubling; spectroscope differs
Chrome Diopside vs Chrome Tourmaline — how do you tell them apart?	Chrome diopside: biaxial −, RI 1.664–1.730, SG 3.22–3.38; Chrome tourmaline: uniaxial −, RI 1.624–1.660, SG 3.00–3.20. SG and optic character separate
Chrome Diopside vs Enstatite — how do you tell them apart?	Chrome diopside: RI 1.664–1.730, SG 3.22–3.38, biaxial −; Enstatite: RI 1.663–1.673, SG 3.20–3.30, biaxial +. Optic sign separates; spectroscope shows chromium lines in chrome diopside
Chrome Diopside vs Hiddenite — how do you tell them apart?	Hiddenite (spodumene): RI 1.660–1.676, SG 3.15–3.21, biaxial +; Chrome diopside: RI 1.664–1.730, SG 3.22–3.38, biaxial −. Optic sign and SG separate
Chrome Tourmaline vs Emerald — how do you tell them apart?	Both green, DR; emerald: RI 1.565–1.602, SG 2.67–2.78; Chrome tourmaline: RI 1.624–1.660, SG 3.00–3.20. SG and RI separate; Chelsea filter: emerald red, chrome tourmaline red or inert
Chrome Tourmaline vs Green Tourmaline — how do you tell them apart?	Same species — chrome tourmaline colored by chromium (Chelsea filter: red), green tourmaline by iron/vanadium (Chelsea filter: inert). Spectroscope shows chromium lines in chrome variety
Chrome Tourmaline vs Diaspore — how do you tell them apart?	SG separates: 3.30–3.39 (Diaspore) vs 3.00–3.20 (Chrome Tourmaline); RI 1.685–1.752 vs 1.624–1.660
Chrome Tourmaline vs Enstatite — how do you tell them apart?	RI separates: 1.663–1.673 (Enstatite) vs 1.624–1.660 (Chrome Tourmaline); SG 3.20–3.30 vs 3.00–3.20
Clinohumite vs Danburite — how do you tell them apart?	SG separates: 3.13–3.35 (Clinohumite) vs 2.97–3.02 (Danburite); RI 1.625–1.675 vs 1.627–1.636
Clinohumite vs Diaspore — how do you tell them apart?	RI separates: 1.625–1.675 (Clinohumite) vs 1.685–1.752 (Diaspore); SG 3.13–3.35 vs 3.30–3.39
Clinohumite vs Jadeite — how do you tell them apart?	Optic character differs: DR (biaxial +) (Clinohumite) vs AGG (Jadeite); RI 1.625–1.675 vs 1.654–1.688, SG 3.13–3.35 vs 3.24–3.43
Clinohumite vs Kornerupine — how do you tell them apart?	Optic character differs: DR (biaxial +) (Clinohumite) vs DR (biaxial −) (Kornerupine); RI 1.625–1.675 vs 1.660–1.699, SG 3.13–3.35 vs 3.27–3.45
Chrysoberyl vs Yellow Sapphire — how do you tell them apart?	Chrysoberyl: RI 1.746–1.755, SG 3.70–3.78, biaxial positive; Yellow sapphire: RI 1.762–1.770, SG 3.99–4.01, uniaxial negative. RI overlap but SG and optic character separate
Chrysoberyl vs Grossular Garnet — how do you tell them apart?	Grossular garnet: SR, RI 1.734–1.759, SG 3.57–3.73; Chrysoberyl: DR (biaxial +), RI 1.746–1.755, SG 3.70–3.78. Polariscope separates — garnet is SR
Chrysoberyl vs Kyanite — how do you tell them apart?	SG separates: 3.53–3.68 (Kyanite) vs 3.70–3.78 (Chrysoberyl); RI 1.712–1.734 vs 1.746–1.755
Chrysoberyl vs Low-Type Zircon — how do you tell them apart?	Low-Type Zircon is SR, Chrysoberyl is DR (biaxial +) — polariscope separates; RI 1.780–1.815 vs 1.746–1.755, SG 3.90–4.10 vs 3.70–3.78
Chrysoberyl vs Malaya / Umbalite Garnet — how do you tell them apart?	Malaya / Umbalite Garnet is SR, Chrysoberyl is DR (biaxial +) — polariscope separates; RI 1.730–1.780 vs 1.746–1.755, SG 3.65–3.87 vs 3.70–3.78
Chrysocolla vs Turquoise — how do you tell them apart?	Turquoise: RI 1.610–1.650, waxy luster, Mohs 5–6; Chrysocolla: RI 1.460–1.570, glassy to resinous, Mohs 2–4
Chrysocolla vs Malachite — how do you tell them apart?	Malachite shows distinctive banded green concentric patterns and higher SG (3.60–4.05 vs 2.00–2.40 for chrysocolla); RI 1.655–1.909 vs 1.460–1.570
Chrysoprase vs Nephrite — how do you tell them apart?	Nephrite: RI 1.600–1.641, fibrous texture under magnification, SG 2.90–3.10; Chrysoprase: RI 1.530–1.544, chalcedony microstructure, SG 2.58–2.64
Chrysoprase vs Prehnite — how do you tell them apart?	Chrysoprase (chalcedony): RI 1.530–1.543, SG 2.58–2.64, AGG; Prehnite: RI 1.611–1.665, SG 2.82–2.94, DR. RI separates
Chrysoprase vs Variscite — how do you tell them apart?	Chrysoprase: RI 1.530–1.543, SG 2.58–2.64, AGG; Variscite: RI 1.560–1.590, SG 2.40–2.60, DR. RI may separate; SG overlaps. Structure (chalcedony vs crystalline) differs
Chrysoprase vs Moldavite — how do you tell them apart?	Moldavite is SR, Chrysoprase is AGG — polariscope separates; RI 1.480–1.510 vs 1.530–1.543, SG 2.32–2.38 vs 2.58–2.64
Citrine vs Yellow Sapphire — how do you tell them apart?	Citrine: RI 1.544–1.553, SG 2.63–2.65; Yellow sapphire: RI 1.762–1.770, SG 3.99–4.01. RI and SG clearly separate
Citrine vs Topaz — how do you tell them apart?	Citrine: RI 1.544–1.553, SG 2.63–2.65, uniaxial +; Yellow topaz: RI 1.609–1.643, SG 3.49–3.57, biaxial +. SG is fastest separator (heft test works)
Citrine vs Heliodor — how do you tell them apart?	Citrine: RI 1.544–1.553, SG 2.63–2.65, uniaxial +; Heliodor (beryl): RI 1.568–1.580, SG 2.68–2.74, uniaxial −. RI overlap; optic sign separates
Citrine vs Scapolite — how do you tell them apart?	Scapolite: RI 1.540–1.572, SG 2.50–2.74, uniaxial −; Citrine: RI 1.544–1.553, SG 2.63–2.65, uniaxial +. Optic sign separates
Citrine vs Smoky Quartz — how do you tell them apart?	RI 1.544–1.553 (Smoky Quartz) vs 1.544–1.553 (Citrine); SG 2.63–2.65 vs 2.63–2.65. Inclusions and spectroscope may be needed
Color-Change Garnet vs Color-Change Sapphire — how do you tell them apart?	Color-change garnet: SR, RI 1.740–1.765, SG 3.65–3.80; Color-change sapphire: DR (uniaxial −), RI 1.762–1.770, SG 3.99–4.01. Polariscope is diagnostic
Color-Change Garnet vs Grossular Garnet — how do you tell them apart?	RI 1.734–1.759 (Grossular Garnet) vs 1.740–1.765 (Color-Change Garnet); SG 3.57–3.73 vs 3.65–3.80. Inclusions and spectroscope may be needed
Color-Change Garnet vs Low-Type Zircon — how do you tell them apart?	SG separates: 3.90–4.10 (Low-Type Zircon) vs 3.65–3.80 (Color-Change Garnet); RI 1.780–1.815 vs 1.740–1.765
Color-Change Garnet vs Padparadscha Sapphire — how do you tell them apart?	Padparadscha Sapphire is DR (uniaxial −), Color-Change Garnet is SR — polariscope separates; RI 1.762–1.770 vs 1.740–1.765, SG 3.95–4.03 vs 3.65–3.80
Color-Change Sapphire vs Synthetic Color-Change Corundum — how do you tell them apart?	Same species properties (RI 1.762–1.770, SG 3.97–4.05). Curved striae, gas bubbles, and fluorescence pattern identify synthetic. Lab certification recommended
Color-Change Sapphire vs Diaspore — how do you tell them apart?	SG separates: 3.99–4.01 (Color-Change Sapphire) vs 3.30–3.39 (Diaspore); RI 1.762–1.770 vs 1.685–1.752
Color-Change Sapphire vs Star Garnet — how do you tell them apart?	Star Garnet is SR, Color-Change Sapphire is DR (uniaxial −) — polariscope separates; RI 1.770–1.830 vs 1.762–1.770, SG 3.93–4.30 vs 3.99–4.01
Coral vs Danburite — how do you tell them apart?	SG separates: 2.97–3.02 (Danburite) vs 2.60–2.70 (Coral); RI 1.627–1.636 vs 1.486–1.658
Coral vs Fire Opal — how do you tell them apart?	Fire Opal is SR, Coral is AGG — polariscope separates; RI 1.370–1.470 vs 1.486–1.658, SG 1.98–2.20 vs 2.60–2.70
Coral vs Goshenite — how do you tell them apart?	Optic character differs: DR (uniaxial −) (Goshenite) vs AGG (Coral); RI 1.577–1.583 vs 1.486–1.658, SG 2.68–2.80 vs 2.60–2.70
Coral vs Grandidierite — how do you tell them apart?	SG separates: 2.85–2.98 (Grandidierite) vs 2.60–2.70 (Coral); RI 1.590–1.623 vs 1.486–1.658
Coral vs Hackmanite — how do you tell them apart?	Hackmanite is SR, Coral is AGG — polariscope separates; RI 1.483–1.487 vs 1.486–1.658, SG 2.14–2.40 vs 2.60–2.70
Cubic Zirconia vs Diamond — how do you tell them apart?	CZ: RI 2.150–2.180, SG 5.60–6.00, no birefringence; Diamond: RI 2.417, SG 3.50–3.53. SG is fastest separator (CZ is much heavier); thermal tester is definitive
Danburite vs Topaz — how do you tell them apart?	Danburite: RI 1.627–1.636, SG 2.97–3.02, biaxial −; Topaz: RI 1.609–1.643, SG 3.49–3.57, biaxial +. SG clearly separates (2.97–3.02 vs 3.49–3.57)
Danburite vs Howlite — how do you tell them apart?	SG separates: 2.97–3.02 (Danburite) vs 2.45–2.58 (Howlite); RI 1.627–1.636 vs 1.583–1.608
Danburite vs Kunzite — how do you tell them apart?	SG separates: 3.15–3.21 (Kunzite) vs 2.97–3.02 (Danburite); RI 1.660–1.676 vs 1.627–1.636
Danburite vs Phenakite — how do you tell them apart?	RI separates: 1.654–1.670 (Phenakite) vs 1.627–1.636 (Danburite); SG 2.95–2.97 vs 2.97–3.02
Demantoid Garnet vs Sphene — how do you tell them apart?	Demantoid: SR, RI 1.880–1.895, SG 3.82–3.88; Sphene: DR (biaxial +), RI 1.843–2.110, SG 3.45–3.55. Polariscope separates; sphene shows extreme birefringence
Demantoid Garnet vs Peridot — how do you tell them apart?	Demantoid: SR, RI 1.880–1.895, SG 3.82–3.88; Peridot: DR (biaxial +), RI 1.654–1.690, SG 3.27–3.48. RI clearly separates; demantoid has diagnostic horsetail inclusions
Demantoid Garnet vs Malachite — how do you tell them apart?	Demantoid Garnet is SR, Malachite is DR (biaxial −) — polariscope separates; RI 1.880–1.895 vs 1.655–1.909, SG 3.82–3.88 vs 3.60–4.05
Diamond vs Moissanite — how do you tell them apart?	Moissanite: RI 2.648–2.691, SG 3.20–3.22, DR (uniaxial +), facet doubling visible; Diamond: RI 2.417, SG 3.50–3.53, SR. Facet doubling and thermal tester separate
Diamond vs White Sapphire — how do you tell them apart?	White sapphire: RI 1.762–1.770, SG 3.99–4.01, DR, no dispersion fire; Diamond: RI 2.417, SG 3.50–3.53, SR, strong dispersion. RI and dispersion separate
Diamond vs Zircon — how do you tell them apart?	Zircon: RI 1.925–1.984, SG 4.60–4.80, DR (strong facet doubling); Diamond: RI 2.417, SG 3.50–3.53, SR. Facet doubling in zircon is diagnostic
Diamond vs Rock Crystal — how do you tell them apart?	Diamond: RI 2.417, SG 3.50–3.53, SR, extreme brilliance and fire; Rock crystal: RI 1.544–1.553, SG 2.63–2.65, DR. Every property differs
Diamond vs Pink Diamond — how do you tell them apart?	RI 2.417 (Pink Diamond) vs 2.417 (Diamond); SG 3.51–3.53 vs 3.50–3.53. Inclusions and spectroscope may be needed
Diaspore vs Enstatite — how do you tell them apart?	RI separates: 1.663–1.673 (Enstatite) vs 1.685–1.752 (Diaspore); SG 3.20–3.30 vs 3.30–3.39
Diaspore vs Low-Type Zircon — how do you tell them apart?	Low-Type Zircon is SR, Diaspore is DR (biaxial +) — polariscope separates; RI 1.780–1.815 vs 1.685–1.752, SG 3.90–4.10 vs 3.30–3.39
Emerald vs Tsavorite Garnet — how do you tell them apart?	Tsavorite is SR, emerald is DR (uniaxial −). SG: 3.59–3.65 vs 2.67–2.78. Polariscope and SG separate
Emerald vs Green Tourmaline — how do you tell them apart?	Both green, DR, uniaxial −; emerald RI 1.565–1.602 vs green tourmaline 1.616–1.650. SG: 2.67–2.78 vs 3.00–3.10. SG clearly separates
Emerald vs Peridot — how do you tell them apart?	Peridot: biaxial +, RI 1.654–1.690, SG 3.27–3.48, strong facet doubling; Emerald: uniaxial −, RI 1.565–1.602, SG 2.67–2.78. RI and SG separate
Emerald vs Hiddenite — how do you tell them apart?	Hiddenite: RI 1.660–1.676, SG 3.15–3.21, biaxial +; Emerald: RI 1.565–1.602, SG 2.67–2.78, uniaxial −. RI and SG clearly separate
Enstatite vs Green Tourmaline — how do you tell them apart?	SG separates: 3.20–3.30 (Enstatite) vs 3.00–3.10 (Green Tourmaline); RI 1.663–1.673 vs 1.616–1.650
Fire Opal vs Opal — how do you tell them apart?	Same species; fire opal lacks play of color, shows body color (orange-red); precious opal shows play of color. Fire opal: often transparent vs opal: translucent
Fire Opal vs Fluorite — how do you tell them apart?	SG separates: 1.98–2.20 (Fire Opal) vs 3.17–3.19 (Fluorite); RI 1.370–1.470 vs 1.432–1.436
Fire Opal vs Hackmanite — how do you tell them apart?	RI separates: 1.370–1.470 (Fire Opal) vs 1.483–1.487 (Hackmanite); SG 1.98–2.20 vs 2.14–2.40
Fluorite vs Opal — how do you tell them apart?	SG separates: 3.17–3.19 (Fluorite) vs 1.98–2.25 (Opal); RI 1.432–1.436 vs 1.370–1.470
Goshenite vs White Sapphire — how do you tell them apart?	Goshenite (beryl): RI 1.577–1.583, SG 2.68–2.80, uniaxial −; White sapphire: RI 1.762–1.770, SG 3.99–4.01, uniaxial −. RI and SG clearly separate
Goshenite vs Rock Crystal — how do you tell them apart?	Rock crystal (quartz): RI 1.544–1.553, SG 2.63–2.65, uniaxial +; Goshenite (beryl): RI 1.577–1.583, SG 2.68–2.80, uniaxial −. RI and optic sign separate
Goshenite vs Howlite — how do you tell them apart?	SG separates: 2.68–2.80 (Goshenite) vs 2.45–2.58 (Howlite); RI 1.577–1.583 vs 1.583–1.608
Goshenite vs Nephrite — how do you tell them apart?	SG separates: 2.68–2.80 (Goshenite) vs 2.90–3.03 (Nephrite); RI 1.577–1.583 vs 1.600–1.627
Goshenite vs Rainbow Moonstone — how do you tell them apart?	RI separates: 1.559–1.572 (Rainbow Moonstone) vs 1.577–1.583 (Goshenite); SG 2.68–2.72 vs 2.68–2.80
Grandidierite vs Larimar — how do you tell them apart?	Optic character differs: DR (biaxial +) (Larimar) vs DR (biaxial −) (Grandidierite); RI 1.595–1.640 vs 1.590–1.623, SG 2.74–2.90 vs 2.85–2.98
Green Tourmaline vs Tsavorite Garnet — how do you tell them apart?	Tsavorite is SR, green tourmaline is DR (uniaxial −). Polariscope separates; RI: 1.730–1.760 vs 1.616–1.650
Grossular Garnet vs Hessonite Garnet — how do you tell them apart?	Same species — hessonite is the orange-cinnamon variety of grossular; green grossular (tsavorite excluded) is typically lighter. Properties overlap; color is the differentiator
Grossular Garnet vs White Sapphire — how do you tell them apart?	White Sapphire is DR (uniaxial −), Grossular Garnet is SR — polariscope separates; RI 1.762–1.770 vs 1.734–1.759, SG 3.99–4.01 vs 3.57–3.73
Hackmanite vs Opal — how do you tell them apart?	RI separates: 1.483–1.487 (Hackmanite) vs 1.370–1.470 (Opal); SG 2.14–2.40 vs 1.98–2.25
Hackmanite vs Sodalite — how do you tell them apart?	Hackmanite is SR, Sodalite is AGG — polariscope separates; RI 1.483–1.487 vs 1.483–1.487, SG 2.14–2.40 vs 2.14–2.40
Hauyne vs Iolite — how do you tell them apart?	Hauyne is SR, Iolite is DR (biaxial −) — polariscope separates; RI 1.494–1.509 vs 1.535–1.547, SG 2.44–2.50 vs 2.57–2.66
Hauyne vs Sodalite — how do you tell them apart?	Sodalite is AGG, Hauyne is SR — polariscope separates; RI 1.483–1.487 vs 1.494–1.509, SG 2.14–2.40 vs 2.44–2.50
Heliodor vs Sapphire (Yellow) — how do you tell them apart?	Yellow sapphire: RI 1.762–1.778, SG 3.99–4.01, uniaxial negative, harder (Mohs 9); Heliodor: RI 1.568–1.580, SG 2.66–2.87, Mohs 7.5–8. SG and RI clearly differentiate
Heliodor vs Yellow Sapphire — how do you tell them apart?	Heliodor (beryl): RI 1.568–1.580, SG 2.68–2.74; Yellow sapphire: RI 1.762–1.770, SG 3.99–4.01. RI and SG clearly separate
Hessonite Garnet vs Malaya / Umbalite Garnet — how do you tell them apart?	Both SR; hessonite RI 1.730–1.760 vs malaya 1.730–1.780. SG: hessonite 3.59–3.65 vs malaya 3.65–3.87. Hessonite shows diagnostic ‘heat-wave’ (roiled) inclusion pattern
Hessonite Garnet vs Star Ruby — how do you tell them apart?	Star Ruby is DR (uniaxial −), Hessonite Garnet is SR — polariscope separates; RI 1.762–1.770 vs 1.730–1.760, SG 3.97–4.05 vs 3.59–3.65
Hessonite Garnet vs Thulite — how do you tell them apart?	Thulite is DR (biaxial +), Hessonite Garnet is SR — polariscope separates; RI 1.691–1.704 vs 1.730–1.760, SG 3.10–3.38 vs 3.59–3.65
Hessonite Garnet vs White Sapphire — how do you tell them apart?	White Sapphire is DR (uniaxial −), Hessonite Garnet is SR — polariscope separates; RI 1.762–1.770 vs 1.730–1.760, SG 3.99–4.01 vs 3.59–3.65
Hiddenite vs Kunzite — how do you tell them apart?	Same species (spodumene); kunzite is pink (Mn), hiddenite is green (Cr). Properties identical; color and spectroscope separate
Howlite vs Turquoise — how do you tell them apart?	Dyed howlite is the most common turquoise imitation. Howlite: RI 1.583–1.608, SG 2.45–2.58; Turquoise: RI 1.610–1.650, SG 2.60–2.90. SG and hot needle test (howlite smells acrid when dyed) separate
Howlite vs Rainbow Moonstone — how do you tell them apart?	SG separates: 2.68–2.72 (Rainbow Moonstone) vs 2.45–2.58 (Howlite); RI 1.559–1.572 vs 1.583–1.608
Indicolite vs Paraíba Tourmaline (Copper-bearing) — how do you tell them apart?	Paraíba: neon blue-green color from copper (Cu), may show EDXRF Cu peak; Indicolite: blue from iron (Fe), no copper. Properties otherwise similar — lab testing (EDXRF) needed for definitive separation
Indicolite vs Sapphire — how do you tell them apart?	Indicolite (tourmaline): RI 1.624–1.644, SG 3.02–3.10; Sapphire: RI 1.762–1.770, SG 3.95–4.03. RI and SG clearly separate
Iolite vs Tanzanite — how do you tell them apart?	Iolite: RI 1.535–1.547, SG 2.57–2.66; Tanzanite: RI 1.691–1.700, SG 3.35. RI and SG clearly separate
Iolite vs Topaz — how do you tell them apart?	Iolite: RI 1.542–1.551, SG 2.53–2.65, biaxial negative, strong trichroism; Blue topaz: RI 1.619–1.627, SG 3.49–3.57, biaxial positive. SG is decisive separator
Jadeite vs Nephrite — how do you tell them apart?	Nephrite: RI 1.600–1.641, fibrous interlocking texture under magnification, SG 2.90–3.10; Jadeite: RI 1.654–1.688, granular interlocking texture, SG 3.24–3.43. SG spot test is fastest separator
Jadeite vs Serpentine / Bowenite — how do you tell them apart?	Serpentine: RI 1.560–1.571, SG 2.44–2.62, much softer (Mohs 3–4); Jadeite: RI 1.654–1.688, SG 3.24–3.43, Mohs 6.5–7. Knife scratch easily separates
Jadeite vs Jet — how do you tell them apart?	Jet is SR, Jadeite is AGG — polariscope separates; RI 1.640–1.680 vs 1.654–1.688, SG 1.10–1.40 vs 3.24–3.43
Jadeite vs Phenakite — how do you tell them apart?	SG separates: 2.95–2.97 (Phenakite) vs 3.24–3.43 (Jadeite); RI 1.654–1.670 vs 1.654–1.688
Jadeite vs Star Diopside — how do you tell them apart?	Optic character differs: DR (biaxial −) (Star Diopside) vs AGG (Jadeite); RI 1.664–1.721 vs 1.654–1.688, SG 3.27–3.36 vs 3.24–3.43
Jadeite vs Tanzanite — how do you tell them apart?	RI separates: 1.691–1.700 (Tanzanite) vs 1.654–1.688 (Jadeite); SG 3.35–3.38 vs 3.24–3.43
Jet vs Onyx — how do you tell them apart?	Jet: RI ~1.640–1.680, SG 1.10–1.35 (dramatically lighter); Onyx: RI 1.530–1.543, SG 2.58–2.64. Heft test is immediately diagnostic
Jet vs Nephrite — how do you tell them apart?	Jet is SR, Nephrite is AGG — polariscope separates; RI 1.640–1.680 vs 1.600–1.627, SG 1.10–1.40 vs 2.90–3.03
Jet vs Pearl — how do you tell them apart?	Jet is SR, Pearl is AGG — polariscope separates; RI 1.640–1.680 vs 1.520–1.690, SG 1.10–1.40 vs 2.60–2.85
Jet vs Star Diopside — how do you tell them apart?	Jet is SR, Star Diopside is DR (biaxial −) — polariscope separates; RI 1.640–1.680 vs 1.664–1.721, SG 1.10–1.40 vs 3.27–3.36
Kornerupine vs Sinhalite — how do you tell them apart?	Both biaxial; kornerupine: RI 1.660–1.699, SG 3.27–3.45, biaxial −; Sinhalite: RI 1.665–1.712, SG 3.47–3.50, biaxial −. Close RI overlap; SG may separate at extremes
Kunzite vs Topaz (Pink) — how do you tell them apart?	Pink topaz: RI 1.619–1.627, SG 3.49–3.57, biaxial positive, perfect basal cleavage; Kunzite: RI 1.660–1.676, SG 3.15–3.23, biaxial positive. SG and cleavage direction differentiate
Kunzite vs Morganite — how do you tell them apart?	Kunzite (spodumene): RI 1.660–1.676, SG 3.15–3.21, biaxial +, strong pleochroism; Morganite (beryl): RI 1.572–1.600, SG 2.71–2.85, uniaxial −. SG and RI separate
Kunzite vs Pink Sapphire — how do you tell them apart?	Kunzite: RI 1.660–1.676, SG 3.15–3.21, biaxial +; Pink sapphire: RI 1.762–1.770, SG 3.98–4.01, uniaxial −. RI clearly separates
Kunzite vs Tanzanite — how do you tell them apart?	SG separates: 3.35–3.38 (Tanzanite) vs 3.15–3.21 (Kunzite); RI 1.691–1.700 vs 1.660–1.676
Kunzite vs Thulite — how do you tell them apart?	RI separates: 1.691–1.704 (Thulite) vs 1.660–1.676 (Kunzite); SG 3.10–3.38 vs 3.15–3.21
Kyanite vs Sapphire — how do you tell them apart?	Polariscope separates: kyanite is biaxial negative, sapphire is uniaxial negative; kyanite RI 1.712–1.734 vs sapphire 1.762–1.770
Kyanite vs Tanzanite — how do you tell them apart?	SG separates: 3.35–3.38 (Tanzanite) vs 3.53–3.68 (Kyanite); RI 1.691–1.700 vs 1.712–1.734
Kyanite vs White Sapphire — how do you tell them apart?	SG separates: 3.99–4.01 (White Sapphire) vs 3.53–3.68 (Kyanite); RI 1.762–1.770 vs 1.712–1.734
Labradorite vs Sunstone — how do you tell them apart?	Both feldspars; sunstone: RI 1.537–1.572, SG 2.62–2.65, aventurescence from copper/hematite platelets; Labradorite: RI 1.559–1.573, SG 2.68–2.75, shows labradorescence (spectral play)
Labradorite vs Moonstone — how do you tell them apart?	Moonstone (orthoclase): RI 1.518–1.526, SG 2.56–2.59, adularescence; Labradorite: RI 1.559–1.573, SG 2.68–2.75. RI clearly separates
Labradorite vs Onyx — how do you tell them apart?	SG separates: 2.58–2.64 (Onyx) vs 2.68–2.75 (Labradorite); RI 1.530–1.543 vs 1.559–1.573
Lapis Lazuli vs Sodalite — how do you tell them apart?	Lapis lazuli: RI ~1.500, SG 2.50–3.00, typically shows gold pyrite flecks; Sodalite: RI 1.483–1.487, SG 2.14–2.30, no pyrite, fluoresces orange under UV
Lapis Lazuli vs Tanzanite — how do you tell them apart?	SG separates: 3.35–3.38 (Tanzanite) vs 2.70–2.90 (Lapis Lazuli); RI 1.691–1.700 vs 1.500–1.670
Larimar vs Turquoise — how do you tell them apart?	Larimar (pectolite): RI 1.595–1.640, SG 2.74–2.90, biaxial +, typically blue-white pattern; Turquoise: RI 1.610–1.650, SG 2.60–2.90, AGG, often shows matrix veining
Low-Type Zircon vs Spessartite Garnet — how do you tell them apart?	SG separates: 4.12–4.18 (Spessartite Garnet) vs 3.90–4.10 (Low-Type Zircon); RI 1.790–1.815 vs 1.780–1.815
Low-Type Zircon vs Sphene — how do you tell them apart?	Sphene is DR (biaxial +), Low-Type Zircon is SR — polariscope separates; RI 1.843–2.110 vs 1.780–1.815, SG 3.45–3.55 vs 3.90–4.10
Low-Type Zircon vs YAG — how do you tell them apart?	SG separates: 4.50–4.60 (YAG) vs 3.90–4.10 (Low-Type Zircon); RI 1.833 vs 1.780–1.815
Malachite vs Sphene — how do you tell them apart?	SG separates: 3.45–3.55 (Sphene) vs 3.60–4.05 (Malachite); RI 1.843–2.110 vs 1.655–1.909
Malachite vs YAG — how do you tell them apart?	YAG is SR, Malachite is DR (biaxial −) — polariscope separates; RI 1.833 vs 1.655–1.909, SG 4.50–4.60 vs 3.60–4.05
Malachite vs Zircon — how do you tell them apart?	SG separates: 4.60–4.80 (Zircon) vs 3.60–4.05 (Malachite); RI 1.925–1.984 vs 1.655–1.909
Malaya / Umbalite Garnet vs Spessartite Garnet — how do you tell them apart?	Both SR; spessartite RI 1.790–1.815 vs malaya 1.730–1.780. SG: spessartite 4.12–4.18 vs malaya 3.65–3.87. SG clearly separates
Moldavite vs Moonstone — how do you tell them apart?	Moldavite is SR, Moonstone is DR (biaxial −) — polariscope separates; RI 1.480–1.510 vs 1.518–1.526, SG 2.32–2.38 vs 2.56–2.59
Moonstone vs Rainbow Moonstone — how do you tell them apart?	Moonstone (orthoclase): RI 1.518–1.526, SG 2.56–2.59; Rainbow moonstone (labradorite): RI 1.559–1.572, SG 2.68–2.72. RI and SG separate; rainbow moonstone shows broader spectral play
Moonstone vs Opal — how do you tell them apart?	Opal: RI 1.370–1.470, SG 1.98–2.25, SR, play of color; Moonstone: RI 1.518–1.526, SG 2.56–2.59, DR, adularescence. RI and optical phenomenon differ
Morganite vs Rose Quartz — how do you tell them apart?	Morganite (beryl): RI 1.572–1.600, SG 2.71–2.85, uniaxial −; Rose quartz: RI 1.544–1.553, SG 2.63–2.65, uniaxial +. RI and optic sign separate
Nephrite vs Serpentine / Bowenite — how do you tell them apart?	Serpentine: RI 1.560–1.571, SG 2.44–2.62, softer (Mohs 3–4); Nephrite: RI 1.600–1.641, SG 2.90–3.10, Mohs 6–6.5. Knife scratch test is diagnostic
Nephrite vs Phenakite — how do you tell them apart?	RI separates: 1.654–1.670 (Phenakite) vs 1.600–1.627 (Nephrite); SG 2.95–2.97 vs 2.90–3.03
Obsidian vs Onyx — how do you tell them apart?	Obsidian: RI 1.480–1.510, SG 2.30–2.60, SR, conchoidal fracture, glassy luster; Onyx (chalcedony): RI 1.530–1.543, SG 2.58–2.64, AGG, waxy luster. Luster and fracture differ
Padparadscha Sapphire vs Spessartite Garnet — how do you tell them apart?	Spessartite Garnet is SR, Padparadscha Sapphire is DR (uniaxial −) — polariscope separates; RI 1.790–1.815 vs 1.762–1.770, SG 4.12–4.18 vs 3.95–4.03
Pearl vs Phenakite — how do you tell them apart?	SG separates: 2.95–2.97 (Phenakite) vs 2.60–2.85 (Pearl); RI 1.654–1.670 vs 1.520–1.690
Pearl vs Star Diopside — how do you tell them apart?	SG separates: 3.27–3.36 (Star Diopside) vs 2.60–2.85 (Pearl); RI 1.664–1.721 vs 1.520–1.690
Peridot vs Sinhalite — how do you tell them apart?	Sinhalite: RI 1.665–1.712, SG 3.47–3.50; Peridot: RI 1.654–1.690, SG 3.27–3.48. RI overlap but SG separates at upper end; sinhalite lacks peridot's strong doubling
Peridot vs Prehnite — how do you tell them apart?	Prehnite: RI 1.611–1.665, SG 2.82–2.94; Peridot: RI 1.654–1.690, SG 3.27–3.48. SG clearly separates; peridot shows strong facet doubling
Pink Diamond vs Sphalerite — how do you tell them apart?	SG separates: 3.51–3.53 (Pink Diamond) vs 3.90–4.10 (Sphalerite); RI 2.417 vs 2.369–2.500
Pink Sapphire vs Ruby — how do you tell them apart?	Same species (corundum) — separated by saturation and hue, not instruments. GIA draws the line at medium-dark red; lighter/pinker = pink sapphire
Pink Sapphire vs Spinel — how do you tell them apart?	Spinel is SR, pink sapphire is DR (uniaxial −); spinel RI 1.712–1.736 vs pink sapphire 1.762–1.770. Polariscope separates; SG: 3.57–3.63 vs 3.98–4.01
Pink Sapphire vs Rubellite — how do you tell them apart?	Rubellite (tourmaline): RI 1.624–1.644, SG 3.02–3.10; Pink sapphire: RI 1.762–1.770, SG 3.98–4.01. RI and SG clearly separate
Pink Sapphire vs Rhodolite Garnet — how do you tell them apart?	Rhodolite is SR, pink sapphire is DR; RI 1.740–1.770 vs 1.762–1.770. SG: 3.74–3.94 vs 3.98–4.01. Polariscope and SG separate
Pink Sapphire vs Spessartite Garnet — how do you tell them apart?	Spessartite Garnet is SR, Pink Sapphire is DR (uniaxial −) — polariscope separates; RI 1.790–1.815 vs 1.762–1.770, SG 4.12–4.18 vs 3.98–4.01
Pyrope Garnet vs Rhodolite Garnet — how do you tell them apart?	Both SR garnets with overlapping RI (1.730–1.770). SG may separate: pyrope 3.62–3.87 vs rhodolite 3.74–3.94. Spectroscope: pyrope shows almandine-type spectrum; rhodolite typically shows blend
Pyrope Garnet vs Spinel — how do you tell them apart?	Both SR; pyrope RI 1.730–1.760 vs spinel 1.712–1.736. SG: pyrope 3.62–3.87 vs spinel 3.57–3.63. Close overlap — spectroscope (almandine spectrum in pyrope) and inclusions separate
Red Beryl vs Ruby — how do you tell them apart?	Red beryl: RI 1.564–1.574, SG 2.66–2.70; Ruby: RI 1.762–1.770, SG 3.97–4.05. RI and SG clearly separate
Rhodochrosite vs Rhodonite — how do you tell them apart?	Rhodochrosite: RI 1.600–1.820, SG 3.40–3.72, translucent with banded pink/white, birefringence 0.220; Rhodonite: RI 1.716–1.752, SG 3.57–3.76, opaque with black manganese veining, birefringence 0.010
Rhodochrosite vs Rose Quartz — how do you tell them apart?	Rose quartz: RI 1.544–1.553, SG 2.63–2.65; Rhodochrosite: RI 1.600–1.820, SG 3.40–3.72. SG clearly separates; rhodochrosite shows banding
Rhodochrosite vs YAG — how do you tell them apart?	YAG is SR, Rhodochrosite is DR (uniaxial −) — polariscope separates; RI 1.833 vs 1.600–1.820, SG 4.50–4.60 vs 3.40–3.70
Rhodolite Garnet vs Ruby — how do you tell them apart?	Rhodolite is SR, ruby is DR (uniaxial −); RI 1.740–1.770 (rhodolite) vs 1.762–1.770 (ruby). SG separates: 3.74–3.94 vs 3.97–4.05
Rhodolite Garnet vs Rubellite — how do you tell them apart?	Rhodolite is SR, rubellite is DR (uniaxial −). RI: 1.740–1.770 vs 1.624–1.644. Polariscope and RI separate
Rhodonite vs Thulite — how do you tell them apart?	Thulite (zoisite): RI 1.691–1.700, SG 3.15–3.36; Rhodonite: RI 1.716–1.752, SG 3.57–3.76. SG separates; rhodonite shows diagnostic black manganese veining
Rhodonite vs Star Diopside — how do you tell them apart?	SG separates: 3.27–3.36 (Star Diopside) vs 3.57–3.76 (Rhodonite); RI 1.664–1.721 vs 1.716–1.752
Rock Crystal vs Topaz — how do you tell them apart?	Rock crystal: RI 1.544–1.553, SG 2.63–2.65; Colorless topaz: RI 1.609–1.643, SG 3.49–3.57. SG clearly separates (heft test works)
Rose Quartz vs Thulite — how do you tell them apart?	Rose quartz: RI 1.544–1.553, SG 2.65, usually translucent to transparent; Thulite: RI 1.691–1.700, SG 3.15–3.36, opaque. RI and SG clearly differentiate
Rubellite vs Ruby — how do you tell them apart?	Ruby (corundum): RI 1.762–1.778, SG 3.99–4.01, uniaxial negative, Mohs 9, chromium spectrum; Rubellite (tourmaline): RI 1.624–1.644, SG 3.00–3.26, uniaxial negative, Mohs 7–7.5. RI and SG clearly separate
Rubellite vs Spinel (Red) — how do you tell them apart?	Red spinel: RI 1.712–1.762, SG 3.54–3.63, singly refractive (SR); Rubellite: RI 1.624–1.644, SG 3.00–3.26, doubly refractive. Refractometer and SG separate cleanly
Ruby vs Spinel — how do you tell them apart?	SR (spinel) vs DR (ruby); spinel RI 1.712–1.736 (single reading) vs ruby RI 1.762–1.770 (double reading). Polariscope is diagnostic
Ruby vs Star Ruby — how do you tell them apart?	Same species — star ruby shows 6-rayed asterism from rutile silk; standard gemological properties identical
Sapphire vs Spinel — how do you tell them apart?	Spinel is SR, sapphire is DR (uniaxial −); spinel RI 1.712–1.736 vs sapphire 1.762–1.770. Polariscope and refractometer separate
Sapphire vs Tanzanite — how do you tell them apart?	Tanzanite: RI 1.691–1.700, SG 3.35, biaxial positive, strong trichroism; Sapphire: RI 1.762–1.770, SG 3.95–4.03, uniaxial negative. RI separates
Sapphire vs Synthetic Color-Change Corundum — how do you tell them apart?	Synthetic CC corundum mimics alexandrite but has corundum RI/SG (1.762–1.770 / 3.97–4.05). Curved striae, gas bubbles, and lack of natural inclusions identify synthetic
Spessartite Garnet vs Sphene — how do you tell them apart?	Sphene is DR (biaxial +), Spessartite Garnet is SR — polariscope separates; RI 1.843–2.110 vs 1.790–1.815, SG 3.45–3.55 vs 4.12–4.18
Spessartite Garnet vs YAG — how do you tell them apart?	SG separates: 4.50–4.60 (YAG) vs 4.12–4.18 (Spessartite Garnet); RI 1.833 vs 1.790–1.815
Sphalerite vs Yellow Diamond — how do you tell them apart?	SG separates: 3.90–4.10 (Sphalerite) vs 3.51–3.53 (Yellow Diamond); RI 2.369–2.500 vs 2.417
Sphene vs Zircon — how do you tell them apart?	SG separates: 4.60–4.80 (Zircon) vs 3.45–3.55 (Sphene); RI 1.925–1.984 vs 1.843–2.110
Spinel vs Synthetic Spinel — how do you tell them apart?	Synthetic spinel: RI 1.725–1.728 (narrow range, typically higher than natural), often shows ADR; Natural spinel: RI 1.712–1.736, SR, no ADR. Inclusions are key — synthetic is typically cleaner
Spinel vs Taaffeite — how do you tell them apart?	Taaffeite: DR (uniaxial −), RI 1.719–1.723; Spinel: SR, RI 1.712–1.736. Nearly identical appearance — polariscope is diagnostic (taaffeite shows DR extinction pattern)
Topaz vs Yellow Sapphire — how do you tell them apart?	Topaz: RI 1.609–1.643, SG 3.49–3.57, biaxial positive; Yellow sapphire: RI 1.762–1.770, SG 3.99–4.01, uniaxial negative. RI clearly separates
Topaz vs White Sapphire — how do you tell them apart?	Colorless topaz: RI 1.609–1.643, SG 3.49–3.57, biaxial +; White sapphire: RI 1.762–1.770, SG 3.99–4.01, uniaxial −. RI clearly separates
Tourmaline vs Watermelon Tourmaline — how do you tell them apart?	Same species — watermelon shows pink center with green rim in cross-section. Properties identical; visual pattern is diagnostic
Turquoise vs Variscite — how do you tell them apart?	Variscite: RI 1.560–1.590, SG 2.40–2.60, typically yellowish-green; Turquoise: RI 1.610–1.650, SG 2.60–2.90, typically blue. RI separates; color is usually diagnostic