What’s in a spelling? Well, there is a difference between ‘carats’ and ‘karats’. The main difference is that carats are a weight measurement used to indicate the mass of a gemstone and karats are used to indicate the purity of a metal, as in 18k gold.
One carat is equal to 0.2 grams or 200 milligrams. Since a carat measurement is a weight, gemstones weighing 1 carat can differ dramatically in size. Gemstones have varying specific gravity so a denser gem will be smaller in size than a 1 carat stone of a lower specific gravity. The cutting of a gem also greatly affects the size and appearance of a gem. Some ‘native’ cut gems aim to retain as much weight as possible (since stones are sold by weight) and have really fat ‘bellies’. The underside of the gem is left somewhat rounded and bulbous to retain the weight of the original rough crystal. As a result, the stone may weigh more, but be the same diameter as a lighter stone. Cutting is very important to a gem’s quality, and although a stone with a larger pavilion (the bottom part of the stone) may weigh more, they often have what is called a ‘window’ when you look in the stone. The window appears like a water drop, or a big open area in the middle of the stone, and reduces the sparkle and overall beauty of a stone. Similarly, some stones are cut very shallow. These stones appear larger from the top view than a heavier counterpart. This can be desirable if working with a budget, and with a particular design, but again, a shallow cut can compromise the beauty of the stone. Beauty is in the eye of the beholder, so always view your gemstones in person to ensure that your purchase will make you fall in love over and over again.
One final note about the carat weight of the stone, carat is the one “C” in the “Four C’s” of diamond grading that is not subjective. To get the carat weight, the stone is simply put on a scale. When getting jewellery appraised, if the stone is in a setting, an appraiser will not be able to get an accurate weight on a scale so will take measurements and make an estimate. If only the top view of the stone is visible in the setting, then it is possible that this weight measurement may be off due to variability in cutting. This may affect the appraisers valuation of the piece. In most cases, it is not in the best interest of the jewellery to remove the stone just to get an accurate weight.
Karat with a “k” is a scale to measure purity of metal, primarily gold. Pure gold is designated as 24k or 99.99% pure gold. Most makers are reluctant to work with 24k gold as pure gold is very soft, and does not have the most desirable qualities for everyday wear. To change the working properties of the metal, and the colour, other metals are added to the gold in varying proportions. So if gold is divided into 24 parts, 18 karat gold has 18 parts gold, and 6 parts other metal, 14 karat gold is 14 parts gold, 10 parts other metal, and 10 karat gold is 10 parts gold, and 14 parts other metal. Another way you see jewellery marked is with numbers – for example, a ring stamped 750 is 750 parts per 1000 of fine gold, or 75% fine gold, otherwise known as 18k (18 out of 24 is 75%). The other metals in your gold could be copper, silver, nickel, or palladium (part of the platinum group of metals), but each alloy, or mixture of metal has it’s own recipe. Most metal suppliers don’t reveal their mixture, but must guarantee the gold content is correct. Generally, if more copper is used, you get rose gold. Nickel or palladium create white gold. An relatively even mixture of copper and silver will give you yellow gold, and a little more silver than copper will create the cool green gold.
If you ever have questions regarding the carat of your gems, or the karat of your gold, visit a local jeweller and they should be able to give you some information after a visual inspection.