Loupewise

Dispersão das Gemas — Tabela de Referência do Fogo

Valores de dispersão (o intervalo B–G) para 115 espécies de gemas, ordenados de maior para menor. A dispersão é a propriedade por trás do «fogo» — os lampejos de cor que uma pedra lapidada projeta ao mover-se. A lapidação decide quanto fogo se vê, mas o limite é fixado por esta constante.

Os nomes das gemas aparecem na forma comercial em inglês e levam à ficha detalhada de cada espécie (em inglês).

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Gema	Dispersão (B–G)	Intervalo IR	Caráter Óptico	Dureza
Cinnabar	0.400	2.905–3.256	Uniaxial (+)	2–2.5
Sphalerite	0.156	2.369–2.371	SR	3.5–4
Cuprite	0.155	2.849	SR	3.5–4
Moissanite	0.104	2.648–2.691	Uniaxial (+)	9.25
Cassiterite	0.071	1.997–2.093	Uniaxial (+)	6–7
Cubic Zirconia	0.066	2.150–2.180	SR	8–8.5
Demantoid Garnet	0.057	1.880–1.895	SR	6.5–7
Sphene	0.051	1.843–2.110	Biaxial (+)	5–5.5
Benitoite	0.046	1.757–1.804	Uniaxial (+)	6–6.5
Blue Diamond	0.044	2.417	SR	10
Brown Diamond	0.044	2.417	SR	10
Diamond	0.044	2.417	SR	10
Pink Diamond	0.044	2.417	SR	10
Yellow Diamond	0.044	2.417	SR	10
Zircon	0.039	1.925–1.984	Uniaxial (+)	7.5
Low-Type Zircon	0.038	1.780–1.815	SR	6
Tanzanite	0.030	1.691–1.700	Biaxial (+)	6–7
Grossular Garnet	0.028	1.734–1.759	SR	6.5–7.5
Hessonite Garnet	0.028	1.730–1.760	SR	7–7.5
Tsavorite Garnet	0.028	1.730–1.760	SR	7–7.5
YAG	0.028	1.833	SR	8–8.5
Spessartite Garnet	0.027	1.790–1.815	SR	7–7.5
Color-Change Garnet	0.026	1.740–1.765	SR	7–7.5
Rhodolite Garnet	0.026	1.740–1.770	SR	7–7.5
Malachite	0.025	1.655–1.909	Biaxial (−)	3.5–4
Almandine Garnet	0.024	1.770–1.830	SR	7–7.5
Star Garnet	0.024	1.770–1.830	SR	7–7.5
Malaya / Umbalite Garnet	0.023	1.730–1.780	SR	7–7.5
Clinohumite	0.022	1.625–1.675	Biaxial (+)	6
Pyrope Garnet	0.022	1.730–1.760	SR	7–7.5
Black Spinel	0.020	1.712–1.730	SR	8
Chrome Diopside	0.020	1.664–1.730	Biaxial (+)	5.5–6.5
Diaspore	0.020	1.702–1.752	Biaxial (+)	6.5–7
Kyanite	0.020	1.712–1.734	Biaxial (−)	4.5–7
Opal	0.020	1.370–1.470	SR	5.5–6.5
Peridot	0.020	1.654–1.690	Biaxial (+)	6.5–7
Prehnite	0.020	1.611–1.665	Biaxial (+)	6–6.5
Spinel	0.020	1.712–1.736	SR	7.5–8
Synthetic Spinel	0.020	1.725–1.728	SR	8
Hauyne	0.019	1.494–1.509	SR	5.5–6
Taaffeite	0.019	1.719–1.723	Uniaxial (−)	8–8.5
Color-Change Sapphire	0.018	1.762–1.770	Uniaxial (−)	9
Hackmanite	0.018	1.483–1.487	SR	5.5–6
Kornerupine	0.018	1.660–1.699	Biaxial (−)	6.5
Padparadscha Sapphire	0.018	1.762–1.770	Uniaxial (−)	9
Pink Sapphire	0.018	1.762–1.770	Uniaxial (−)	9
Ruby	0.018	1.762–1.770	Uniaxial (−)	9
Sapphire	0.018	1.762–1.770	Uniaxial (−)	9
Sinhalite	0.018	1.665–1.712	Biaxial (−)	6.5–7
Star Ruby	0.018	1.762–1.770	Uniaxial (−)	9
Star Sapphire	0.018	1.762–1.770	Uniaxial (−)	9
Synthetic Color-Change Corundum	0.018	1.762–1.770	Uniaxial (−)	9
White Sapphire	0.018	1.762–1.770	Uniaxial (−)	9
Yellow Sapphire	0.018	1.762–1.770	Uniaxial (−)	9
Calcite	0.017	1.486–1.658	Uniaxial (−)	3
Chrome Tourmaline	0.017	1.624–1.660	Uniaxial (−)	7–7.5
Danburite	0.017	1.627–1.636	Biaxial (−)	7–7.5
Enstatite	0.017	1.663–1.673	Biaxial (+)	5–5.5
Green Tourmaline	0.017	1.616–1.650	Uniaxial (−)	7–7.5
Hiddenite	0.017	1.660–1.676	Biaxial (+)	6.5–7
Indicolite	0.017	1.624–1.644	Uniaxial (−)	7–7.5
Iolite	0.017	1.540–1.560	Biaxial (−)	7–7.5
Kunzite	0.017	1.660–1.676	Biaxial (+)	6.5–7
Paraiba Tourmaline	0.017	1.624–1.644	Uniaxial (−)	7–7.5
Rubellite	0.017	1.624–1.644	Uniaxial (−)	7–7.5
Scapolite	0.017	1.540–1.572	Uniaxial (−)	6–6.5
Tourmaline	0.017	1.624–1.644	Uniaxial (−)	7–7.5
Watermelon Tourmaline	0.017	1.616–1.650	Uniaxial (−)	7–7.5
Andalusite	0.016	1.629–1.649	Biaxial (−)	7–7.5
Rhodonite	0.016	1.716–1.752	Biaxial (+)	5.5–6.5
Variscite	0.016	1.560–1.594	Biaxial (−)	3.5–4.5
Alexandrite	0.015	1.746–1.755	Biaxial (+)	8.5
Cat's Eye Chrysoberyl	0.015	1.746–1.755	Biaxial (+)	8.5
Chrysoberyl	0.015	1.746–1.755	Biaxial (+)	8.5
Grandidierite	0.015	1.590–1.623	Biaxial (−)	7–7.5
Phenakite	0.015	1.654–1.670	Uniaxial (+)	7.5–8
Rhodochrosite	0.015	1.600–1.820	Uniaxial (−)	3.5–4
Aquamarine	0.014	1.577–1.583	Uniaxial (−)	7.5–8
Emerald	0.014	1.565–1.602	Uniaxial (−)	7.5–8
Goshenite	0.014	1.577–1.583	Uniaxial (−)	7.5–8
Heliodor	0.014	1.568–1.580	Uniaxial (−)	7.5–8
Morganite	0.014	1.572–1.600	Uniaxial (−)	7.5–8
Red Beryl	0.014	1.564–1.574	Uniaxial (−)	7.5–8
Topaz	0.014	1.609–1.643	Biaxial (+)	8
Agate	0.013	1.530–1.543	Agregado	6.5–7
Amethyst	0.013	1.544–1.553	Uniaxial (+)	7
Ametrine	0.013	1.544–1.553	Uniaxial (+)	7
Apatite	0.013	1.628–1.649	Uniaxial (−)	5
Aventurine	0.013	1.544–1.553	Agregado	7
Bloodstone	0.013	1.530–1.543	Agregado	6.5–7
Carnelian	0.013	1.530–1.543	Agregado	6.5–7
Chalcedony	0.013	1.530–1.543	Agregado	6.5–7
Chrysoprase	0.013	1.530–1.543	Agregado	6.5–7
Citrine	0.013	1.544–1.553	Uniaxial (+)	7
Hawk's Eye	0.013	1.544–1.553	Agregado	7
Onyx	0.013	1.530–1.543	Agregado	6.5–7
Prasiolite	0.013	1.544–1.553	Uniaxial (+)	7
Rock Crystal	0.013	1.544–1.553	Uniaxial (+)	7
Rose Quartz	0.013	1.544–1.553	Uniaxial (+)	7
Smoky Quartz	0.013	1.544–1.553	Uniaxial (+)	7
Star Diopside	0.013	1.664–1.721	Biaxial (+)	5–6
Tiger's Eye	0.013	1.544–1.553	Agregado	7
Chrysocolla Chalcedony	0.013	1.530–1.543	Agregado	6.5–7
Amazonite	0.012	1.514–1.530	Biaxial (−)	6–6.5
Labradorite	0.012	1.559–1.573	Biaxial (+)	6–6.5
Moonstone	0.012	1.518–1.526	Biaxial (−)	6–6.5
Rainbow Moonstone	0.012	1.559–1.572	Biaxial (−)	6–6.5
Sunstone	0.012	1.537–1.572	Biaxial (−)	6–6.5
Thulite	0.012	1.691–1.704	Biaxial (+)	6–7
Larimar	0.010	1.595–1.640	Biaxial (+)	4.5–5
Moldavite	0.010	1.480–1.510	SR	5.5
Obsidian	0.010	1.480–1.510	SR	5–5.5
Sugilite	0.010	1.607–1.610	Uniaxial (−)	5.5–6.5
Fluorite	0.007	1.432–1.436	SR	4
Charoite	0.005	1.550–1.559	Agregado	5–6

Que gema tem a dispersão mais alta?
Entre as 132 gemas desta referência, Cinnabar tem a dispersão mais alta (0.400), seguida de Sphalerite (0.156), Cuprite (0.155), Moissanite (0.104). O diamante mede 0.044.

A moissanite tem mais fogo do que o diamante?
Sim: a dispersão da moissanite é 0.104 contra 0.044 do diamante, mais do dobro. Fogo excessivo num suposto diamante é o primeiro sinal prático, confirmado pelo desdobramento das facetas (birrefringência 0.043).

Veja também: Reference Database (EN) · Guide (EN)