Carats Weight Calculator
From: CSG, Computer Support Group, Inc. and CSGNetwork.Com
This script calculates weight conversions between grams of weight and carats, points, kilograms and milligrams. Carats, abbreviated "ct." and spelled with a "c", is a measure of weight used for gemstones. The carat weight was standardized in the 20th century. The United States officially adopted the metric carat in 1913. One carat = .02 grams or 200 milligrams, equal to 1/5 of a gram. Stones are measured to the nearest hundredth of a carat. A hundreth of a carat is also called a point. Thus a .10 carat stone can be called either 10 points, or 1/10 of a carat. Small stones like .05, and .10ct are most often referred to by point designations. The spelling of karat with a "K" is a measure of the purity of a gold alloy, as opposed to stones. A one carat round diamond of average proportions is approximately 6.5mm in diameter. Be aware that this unique relationship of weight and size is different for each family of stones. For example ruby and sapphire gems are both heavier than a diamond; technically, they have a higher specific gravity, so a 1 carat ruby or sapphire is smaller in size than a one carat diamond.
Gemstone Characteristics TableSpecific Gravity: Specific gravity is the number of times heavier a gemstone of any volume is than an equal volume of water; in other words, it is the ratio of the density of the gemstone to the density of water. For all gemstones listed in this table there is a scientifically determined specific gravity. You can use the specific gravity and a couple simple measurements to estimate the carat weight of a stone. We have created a calculator that makes a gemstone carat weight estimation using this principle.
Mohs Hardness: Hardness can be tested through scratching. A mineral can only be scratched by a harder substance. Therefore, a relative scale can be established to account for the differences in hardness simply by seeing which mineral scratches another. That is exactly what French mineralogist Friedrich Mohs proposed almost one hundred and seventy years ago. The Mohs Hardness Scale starting with talc at 1 being the softest and ending with diamond at 10 hardest, is universally used around the world as a way of distinguishing minerals. Simply put - the higher the number, the harder the mineral.
Index of Refraction: All materials refract light, ie alter its angle. The amount by which light is refracted is an important feature of every Gemstone. The measure of a material's refractivity is known as its index of refracton (R.I.). Without going too deeply into physics, light travels at different speeds through different media. When light passes from one medium to another, its path is altered (bent) and it is said to be diffracted.
Gemstone Family Classification: The gemstones listed here show every color in the rainbow. Even with such variety of colors, patterns and shapes - they can be broken down into 16 different families based on their chemical composition.
Gemstone Name Specific Gravity Mohs Hardness Index of Refraction Gemstone Family Achorite 3.03 - 3.25 7.0 - 7.5 Mohs 1.610-1.661 Tourmaline Agate 2.65 7.0 Mohs 1.530 - 1.550 Quartz Alexandrite 3.68 - 3.78 8.5 Mohs 1.746 - 1.755 Chrysoberyl Almandine 3.50 - 4.30 6.5 - 7.5 Mohs 1.750 - 1.830 Garnet Almandine Spinel 3.58 - 4.06 8.0 Mohs 1.708 - 1.735 Spinel Almandine-Spessartine 3.50 - 4.30 6.5 - 7.5 Mohs 1.750 - 1.830 Garnet Amazonite 2.55 - 2.76 6.0 - 6.5 Mohs 1.518 - 1.526 Feldspar Amethyst 2.65 7.0 Mohs 1.532 - 1.554 Quartz Andradite 3.50 - 4.30 6.5 - 7.5 Mohs 1.880 - 1.940 Garnet Aquamarine 2.63 - 2.91 7.5 - 8.0 Mohs 1.567-1.590 Beryl Balas Ruby 3.58 - 4.06 8.0 Mohs 1.708 - 1.735 Spinel Black Opal 1.98 - 2.25 5.5 - 6.5 Mohs 1.440 - 1.460 Opal Bloodstone 2.65 7.0 Mohs 1.535 - 1.539 Quartz Brazilian Emerald 3.03 - 3.25 7.0 - 7.5 Mohs 1.610 - 1.640 Tourmaline Cairngorm 2.65 7.0 Mohs 1.540 - 1.550 Quartz Carnelian 2.65 7.0 Mohs 1.530 - 1.550 Quartz Cat's Eye 3.68 - 3.78 8.5 Mohs 1.746 - 1.755 Chrysoberyl Chalcedony 2.65 7.0 Mohs 1.544 - 1.553 Quartz Chlorspinel 3.58 - 4.06 8.0 Mohs 1.712 - 1.717 Spinel Chrome Pyrope 3.50 - 4.30 6.5 - 7.5 Mohs 1.730 - 1.760 Garnet Chrysoberyl 3.68 - 3.78 8.5 Mohs 1.746 - 1.755 Chrysoberyl Chrysoprase 2.65 7.0 Mohs 1.530 - 1.550 Quartz Citrine 2.65 7.0 Mohs 1.532 - 1.554 Quartz Color-Change Garnet 3.50 - 4.30 6.5 - 7.5 Mohs 1.730 - 1.760 Garnet Demantoid 3.50 - 4.30 6.5 - 7.5 Mohs 1.880 - 1.900 Garnet Diamond 3.51 10 Mohs 2.417 Diamond Dravite 3.03 - 3.25 7.0 - 7.5 Mohs 1.610-1.661 Tourmaline Emerald 2.63 - 2.91 7.5 - 8.0 Mohs 1.560 - 1.605 Beryl Feldspar 2.55 - 2.76 6.0 - 6.5 Mohs 1.518 - 1.572 Feldspar Fire Opal 1.98 - 2.25 5.5 - 6.5 Mohs 1.430 - 1.460 Opal Garnet 3.50 - 4.30 6.5 - 7.5 Mohs 1.730 - 1.760 Garnet Ghanospinel 3.58 - 4.06 8.0 Mohs 1.712 - 1.747 Spinel Goshenite 2.63 - 2.91 7.5 - 8.0 Mohs 1.570 - 1.600 Beryl Green Quartz 2.65 7.0 Mohs 1.540-1.550 Quartz Grossular 3.50 - 4.30 6.5 - 7.5 Mohs 1.880 - 1.940 Garnet Heliodore 2.63 - 2.91 7.5 - 8.0 Mohs 1.570 - 1.600 Beryl Heliotrope 2.65 7.0 Mohs 1.535 - 1.539 Quartz Hessonite 3.50 - 4.30 6.5 - 7.5 Mohs 1.730 - 1.760 Garnet Hyacinth 4.60 - 4.70 7.5 Mohs 1.777 - 1.987 Zircon Indicolite 3.03 - 3.25 7.0 - 7.5 Mohs 1.610 - 1.640 Tourmaline Jade 2.90 - 3.10 6.0 Mohs 1.640 - 1.667 Jade Jadeite 2.90 - 3.10 6.0 Mohs 1.640 - 1.667 Jade Jargon 4.60 - 4.70 7.5 Mohs 1.777 - 1.987 Zircon Jasper 2.65 7.0 Mohs 1.540 - 1.550 Quartz Labradorite 2.55 - 2.76 6.0 - 6.5 Mohs 1.560 - 1.572 Feldspar Lapis Lazuli 2.70 - 2.90 5.0 - 5.5 Mohs 1.500 - 1.550 Lapis Lazuli Malaia 3.50 - 4.30 6.5 - 7.5 Mohs 1.880 - 1.940 Garnet Matura Diamond 4.60 - 4.70 7.5 Mohs 1.777 - 1.987 Zircon Moonstone 2.55 - 2.76 6.0 - 6.5 Mohs 1.518 - 1.526 Feldspar Morganite 2.63 - 2.91 7.5 - 8.0 Mohs 1.585 - 1.594 Beryl Morion 2.65 7.0 Mohs 1.540 - 1.550 Quartz Nephrite 2.90 - 3.10 6.0 Mohs 1.600 - 1.641 Jade Onyx 2.65 7.0 Mohs 1.531 - 1.539 Quartz Opal 1.98 - 2.25 5.5 - 6.5 Mohs 1.440 - 1.460 Opal Orthoclase 2.55 - 2.76 6.0 - 6.5 Mohs 1.518 - 1.526 Feldspar Peridot 3.22 - 3.45 7.0 Mohs 1.635 - 1.690 Peridot Peristerite 2.55 - 2.76 6.0 - 6.5 Mohs 1.560 - 1.572 Feldspar Praziolite 2.65 7.0 Mohs 1.540 - 1.550 Quartz Pyrope 3.50 - 4.30 6.5 - 7.5 Mohs 1.730 - 1.760 Garnet Pyrope-Almandine 3.50 - 4.30 6.5 - 7.5 Mohs 1.730 - 1.760 Garnet Pyrope-Spessartine 3.50 - 4.30 6.5 - 7.5 Mohs 1.730 - 1.760 Garnet Quartz 2.65 7.0 Mohs 1.544 - 1.553 Quartz Red Beryl 2.63 - 2.91 7.5 - 8.0 Mohs 1.570 - 1.598 Beryl Rhodolite 3.50 - 4.30 6.5 - 7.5 Mohs 1.740 - 1.770 Garnet Rock Crystal 2.65 7.0 Mohs 2.000 Quartz Rose Quartz 2.65 7.0 Mohs 1.540 - 1.550 Quartz Rubellite 3.03 - 3.25 7.0 - 7.5 Mohs 1.610 - 1.640 Tourmaline Rubicelle 3.58 - 4.06 8.0 Mohs 1.712 - 1.717 Spinel Ruby 3.96 - 4.05 9.0 Mohs 1.757 - 1.779 Corundum Sapphire 3.96 - 4.05 9.0 Mohs 1.757 - 1.779 Corundum Sapphire Spinel 3.58 - 4.06 8.0 Mohs 1.712 - 1.747 Spinel Siberite 3.03 - 3.25 7.0 - 7.5 Mohs 1.625-1.675 Tourmaline Smoky Quartz 2.65 7.0 Mohs 1.540 - 1.550 Quartz Spessartine 3.50 - 4.30 6.5 - 7.5 Mohs 1.790 - 1.810 Garnet Spinel 3.58 - 4.06 8.0 Mohs 1.712 - 1.717 Spinel Sunstone 2.55 - 2.76 6.0 - 6.5 Mohs 1.560 - 1.572 Feldspar Topaz 3.50 - 3.60 8.0 Mohs 1.607 - 1.627 Topaz Topazolite 3.50 - 4.30 6.5 - 7.5 Mohs 1.880 - 1.940 Garnet Tourmaline 3.03 - 3.25 7.0 - 7.5 Mohs 1.603 - 1.655 Tourmaline Tsavorite 3.50 - 4.30 6.5 - 7.5 Mohs 1.739 - 1.744 Garnet Turquoise 2.60 - 2.80 5.0 - 6.0 Mohs 1.610 - 1.650 Turquoise Uvarovite 3.50 - 4.30 6.5 - 7.5 Mohs 1.740 - 1.870 Garnet Verdilite 3.03 - 3.25 7.0 - 7.5 Mohs 1.612-1.638 Tourmaline Water Opal 1.98 - 2.25 5.5 - 6.5 Mohs 1.440 - 1.460 Opal White Opal 1.98 - 2.25 5.5 - 6.5 Mohs 1.440 - 1.460 Opal Zircon 4.60 - 4.70 7.5 Mohs 1.777 - 1.987 Zircon