Size Charts
ROUND BRILLIANT CUT STONES
Size/Weight Comparison Charts
How to use these charts: Gemstones will vary slightly because of the different densities of the the stone, For example you can see from the first chart that a 6mm round brilliant diamond might weigh 0.90 ct while a 6mm Ruby in an equivalent 6mm size would weigh approximately 1.05 cts. These numbers are estimates only and can vary based on a stones depth, but should still give you a general idea on how density can effect a stones weight.
ROUND BRILLIANT CUT STONES
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| GEMSTONE | 2mm | 3mm | 4mm | 5mm | 6mm | 7mm | 8mm |
| Alexandrite | .04 | .12 | .35 | .63 | 1.30 | 2.15 | 2.90 |
| Amethyst | .04 | .10 | .20 | .40 | .70 | 1.30 | 1.80 |
| Aquamarine | .04 | .10 | .25 | .45 | .75 | 1.60 | 2.40 |
| Citrine | .04 | .10 | .20 | .40 | .70 | 1.30 | 1.80 |
| Diamond | .04 | .10 | .23 | .47 | .90 | 1.35 | 1.90 |
| Emerald | .04 | .12 | .27 | .48 | .80 | 1.70 | 2.50 |
| Garnet | .05 | .13 | .30 | .60 | 1.00 | 1.60 | 2.50 |
| Opal | .02 | .09 | .16 | .34 | .57 | .83 | 1.30 |
| Peridot | .05 | .12 | .26 | .50 | .85 | 1.25 | 2.00 |
| Ruby | .05 | .15 | .34 | .65 | 1.05 | 1.60 | 2.25 |
| Sapphire | .05 | .15 | .34 | .65 | 1.05 | 1.60 | 2.25 |
| Topaz | .04 | .11 | .30 | .56 | 1.00 | 1.55 | 2.50 |
| Tourmaline | .04 | .12 | .24 | .45 | .75 | 1.55 | 2.00 |
| Zircon | .06 | .17 | .36 | .69 | 1.25 | 1.75 | 2.60 |
| OVAL CUT STONES | |||||||||||
| GEMSTONE | 5x3 | 6x4 | 7x5 | 8x6 | 9x7 | 10x8 | 11x9 | 12x10 | 14x10 | 16x12 | 18x13 |
| Alexandrite | .30 | .61 | .80 | 1.45 | 2.00 | 3.60 | 4.25 | 6.00 | 8.90 | 12.50 | 18.00 |
| Amethyst | .23 | .45 | .85 | 1.25 | 1.75 | 2.40 | 3.20 | 4.50 | 6.50 | 11.00 | 14.00 |
| Aquamarine | .20 | .40 | .75 | 1.10 | 1.75 | 2.25 | 3.00 | 4.50 | 6.75 | 10.15 | 10.57 |
| Citrine | .23 | .45 | .85 | 1.25 | 1.75 | 2.40 | 3.25 | 4.20 | 5.20 | 9.00 | 10.75 |
| Diamond | .25 | .50 | .75 | 1.40 | 2.00 | 3.00 | 4.00 | 5.00 | 8.00 | 11.50 | 16.00 |
| Emerald | .28 | .52 | .85 | 1.00 | 1.60 | 2.25 | 3.75 | 5.00 | 7.50 | 12.00 | 14.50 |
| Garnet | .25 | .55 | 1.00 | 1.40 | 2.10 | 2.80 | 3.75 | 5.00 | 7.00 | 10.00 | 13.25 |
| Opal | .16 | .28 | .47 | .75 | 1.10 | 1.65 | 2.15 | 3.00 | 4.00 | 5.25 | 5.75 |
| Peridot | .28 | .50 | .95 | 1.35 | 2.00 | 2.50 | 3.50 | 4.00 | 6.00 | 9.50 | 13.00 |
| Ruby | .35 | .60 | 1.00 | 1.55 | 2.20 | 3.15 | 3.80 | 6.00 | 7.25 | 12.00 | 13.00 |
| Sapphire | .35 | .60 | 1.00 | 1.55 | 2.20 | 3.15 | 3.80 | 6.00 | 7.25 | 12.00 | 13.00 |
| Topaz | .27 | .57 | 1.10 | 1.60 | 2.50 | 3.50 | 4.50 | 6.00 | 8.80 | 12.00 | 17.00 |
| Tourmaline | .25 | .50 | .90 | 1.18 | 2.30 | 2.90 | 3.50 | 5.25 | 6.80 | 8.50 | 12.00 |
| Zircon | .40 | .75 | 1.45 | 2.00 | 2.85 | 4.00 | 5.60 | 7.50 | 8.20 | 13.50 | 14.50 |
| EMERALD CUT STONES | |||||||||||
| GEMSTONE | 5x3 | 6x4 | 7x5 | 8x6 | 9x7 | 10x8 | 11x9 | 12x10 | 14x10 | 16x12 | 18x13 |
| Alexandrite | .40 | .70 | 1.30 | 2.60 | 3.60 | 4.20 | 6.00 | 8.50 | 9.90 | 14.50 | 22.00 |
| Amethyst | .35 | .55 | 1.00 | 1.60 | 2.25 | 2.90 | 4.20 | 5.60 | 7.25 | 13.00 | 17.00 |
| Aquamarine | .25 | .50 | .80 | 1.40 | 2.00 | 3.00 | 4.30 | 4.75 | 7.75 | 13.50 | 17.00 |
| Citrine | .35 | .55 | 1.00 | 1.60 | 2.25 | 2.90 | 4.20 | 5.60 | 7.25 | 13.00 | 17.00 |
| Diamond | .25 | .50 | 1.00 | 1.50 | 3.00 | 4.00 | 5.00 | 7.8 | 8.80 | 13.00 | 20.00 |
| Emerald | .30 | .60 | .90 | 1.80 | 2.31 | 3.15 | 4.50 | 5.25 | 5.80 | 14.00 | 17.50 |
| Garnet | .40 | .80 | 1.20 | 1.70 | 2.50 | 3.50 | 4.30 | 6.35 | 9.00 | 17.50 | 21.00 |
| Peridot | .35 | .60 | 1.00 | 1.70 | 2.25 | 3.80 | 5.25 | 6.25 | 8.80 | 17.00 | 20.00 |
| Ruby | .55 | .75 | 1.15 | 1.75 | 2.30 | 2.75 | 4.00 | 6.25 | 9.00 | 12.50 | 18.70 |
| Sapphire | .55 | .75 | 1.15 | 1.75 | 2.30 | 2.75 | 4.00 | 6.25 | 9.00 | 12.50 | 18.70 |
| Topaz | .40 | .65 | 1.25 | 2.40 | 3.40 | 4.00 | 5.75 | 8.00 | 9.50 | 14.00 | 21.00 |
| Tourmaline | .30 | .60 | 1.60 | 2.15 | 2.80 | 3.60 | 4.30 | 5.20 | 8.50 | 13.00 | 16.50 |
| Zircon | .60 | .80 | 1.70 | 2.35 | 3.90 | 4.50 | 6.20 | 7.05 | 8.95 | 14.30 | 19.90 |
| PEAR CUT STONES | ||||||||
| GEMSTONE | 5x3 | 6x4 | 7x5 | 8x5 | 9x6 | 10x7 | 13x8 | 14x10 |
| Alexandrite | .30 | .50 | .85 | 1.10 | 2.10 | 3.60 | 6.60 | 8.80 |
| Amethyst | .20 | .35 | .65 | .85 | 1.25 | 1.70 | 4.00 | 5.00 |
| Aquamarine | .20 | .35 | .65 | .90 | 1.30 | 1.85 | 4.20 | 5.60 |
| Citrine | .20 | .35 | .65 | .85 | 1.30 | 1.70 | 4.00 | 5.00 |
| Diamond | .25 | .50 | .75 | 1.00 | 1.50 | 2.00 | 3.50 | 5.00 |
| Emerald | .25 | .45 | .70 | 1.05 | 1.70 | 2.60 | 4.15 | 6.10 |
| Garnet | .25 | .40 | 1.00 | 1.15 | 1.30 | 1.80 | 3.50 | 5.80 |
| Opal | .13 | .22 | .35 | .50 | .70 | 1.03 | 1.40 | 2.45 |
| Peridot | .25 | .45 | .70 | .80 | 1.10 | 1.40 | 3.40 | 4.75 |
| Ruby | .30 | .50 | .75 | 1.00 | 1.85 | 2.50 | 4.75 | 7.90 |
| Sapphire | .30 | .50 | .75 | 1.00 | 1.85 | 2.50 | 4.75 | 7.90 |
| Topaz | .25 | .50 | 1.00 | 1.10 | 2.00 | 3.50 | 6.50 | 8.50 |
| Tourmaline | .35 | .45 | .60 | .90 | 1.10 | 1.40 | 2.80 | 6.75 |
| Zircon | .30 | .70 | 1.00 | 1.30 | 2.60 | 4.00 | 5.25 | 7.50 |
| MARQUISE CUT STONES | ||||||
| GEMSTONE | 4x2 | 6x3 | 8x4 | 10x5 | 12x6 | 14x7 |
| Alexandrite | .07 | .30 | .70 | 1.25 | 2.10 | 3.50 |
| Amethyst | .10 | .20 | .48 | .90 | 1.59 | 2.45 |
| Aquamarine | .08 | .20 | .50 | .80 | 1.50 | 2.75 |
| Citrine | .10 | .20 | .50 | .90 | 1.59 | 2.45 |
| Diamond | .12 | .25 | .50 | 1.00 | 2.00 | 3.00 |
| Emerald | .09 | .30 | .60 | 1.10 | 1.80 | 2.80 |
| Garnet | .09 | .25 | .60 | 1.20 | 2.00 | 2.85 |
| Opal | .09 | .17 | .37 | .59 | 1.00 | 1.25 |
| Peridot | .10 | .25 | .50 | 1.00 | 2.00 | 2.55 |
| Ruby | .13 | .35 | .75 | 1.15 | 2.20 | 3.00 |
| Sapphire | .13 | .35 | .75 | 1.15 | 2.20 | 3.00 |
| Topaz | .07 | .30 | .70 | 1.20 | 2.00 | 3.40 |
| Tourmaline | .10 | .30 | .60 | .85 | 1.55 | 2.20 |
| Zircon | .13 | .33 | .75 | 1.25 | 1.95 | 3.00 |
Physical Properties of Gemstones
| Name | Hardness | Chemical Composition | Density |
| Alexandrite | 8.5 | BeAl2O4 | 3.73 |
| Amethyst | 7 | SiO2 | 2.66 |
| Ametrine | 7 | SiO2 | 2.66 |
| Beryl | 7.5 | Be3Al2(SiO3)6 | 2.67-2.745 |
| Chrome Tourmaline |
7-7.5 | (NaCa)(LI,MgFe,Al)9B3Si6(O,OH)31 | 3.06 (.05, +.15) |
| Chrysoberyl | 8.5 | BeAl2O4 | 3.73 |
| Chrysoberyl Cats Eye |
8.5 | BeAl2O4 | 3.73 |
| Diamond | 10 | C | 3.52 |
| Emerald | 7.5-8 | Be3Al2(SiO3)6 | 2.72 (-.05, +.12) |
| Kyanite | 4.5 - 7.0 | AL2SIO5 | 3.56 - 3.68 |
| Malaia Garnet | 7 - 7.5 | [Mg3 + Mn3]AL2(SIO4) |
3.65 - 4.20 |
| Mali Garnet | 7.25 | Ca3Al2(SiO4)3 | 3.65 |
| Opal | 5.5 - 6.0 | SIO2nH2O | 2.65 - 3.00 |
| Peridot | 6.5 | (Mg,Fe)2(SiO)4 | 3.34 |
| Quartz | 7 | SiO2 | 2.65 |
| Ruby | 9 | AL2O3 | 4 |
| Sapphire | 9 | AL22O3 | 4 |
| Spessartite Garnet |
7.25 | Mn3Al2(SiO4)3 | 4.14-4.20 |
| Spinel | 8 | MgAl2O4 | 3.60 (-.03, +.30) |
| Star Sapphire | 9 | AL2O3 | 4 |
| Tanzanite | 6-7 | Ca2(Al,OH)Al2(SIO4) | 3.30 (+.10, -.10) |
| Topaz | 8 | AL(F,OH)2SIO4 | 3.52 - 3.56 |
| Tourmaline | 7-7.5 | (NaCa)(LI,MgFe,Al)9B3Si6(O,OH)31 | 3.06 (.05, +.15) |
| Tsavorite | 7 | Ca3Al2(SiO4)3 | 3.61(-.27, +.12) |
| Turquoise | 5.5-6 | CuAl6(PO4)4(OH)85H2O | 2.60- 2.90 |
| Zircon | 7.5 | ZrSiO4 | 4.00-4.73 |