The Mohs Scale of Mineral Hardness determines a stone’s resistance to scratching. A mineral such as talc may be scratched by anything matching or exceeding its hardness. The higher on the scale a stone is, the less vulnerable it is to abrasions. Diamonds are at the far end, the pinnacle of hardness. At the same time, diamonds are admired for how its cuts draw out its aesthetic properties. Specialized tools are a must for bringing out the best in diamonds.
Only another diamond can scratch another diamond. Among the earliest ways of shaping the jewels was to remove debris and other materials left over from the mining process. While imperfect diamonds were used to polish other materials, it wasn’t until the Middle Ages that diamond dust was used to cut other diamonds.
1456 saw the invention of a specialized wheel called the scaif. This device used a combination of olive oil and diamond dust on polishing wheels to better shape facets and bring out a diamond’s shine. A diagram from the 18th century shows the anatomy of a scaif, with arms to hold stones at precise angles for faceting, allowing for many jewels to be shaped at once.
Diamond’s atomic bonds create durability so strong, “diamond” originates from the ancient Greek word from “unbreakable.” However, from certain angles, the bonds are weaker. When hit against these directions, also known as cleavage planes, the stone will split. Diamond cutters probably started cleaving jewels during the 16th century, allowing a single piece of rough to become multiple faceted jewels.
Diamond saws are also used to divide rough into multiple pieces. Unlike cleaving, saws allow for cuts in multiple directions, as well as giving more control to the diamond cutter. Early versions of the diamond saw consisted of wire coated first in oil and then diamond dust. Modern saws use electroplating, sintering and other methods to attach abrasives.
Lasers were invented in the 1960s and have since been used for a wide range of purposes, including diamond cutting. Instead of scratching, intense heat divides the stone. They may be used when the tiniest cuts are needed, or to avoid excessive vibrations when shaping the jewel. Lasers are also used to place inscriptions onto the girdle or other discrete portions of the diamond to add serial numbers or other forms of identification.
Once a diamond is cut and polished, there’s an optional step. Certification from an independent third party laboratory can help determine if a diamond is cut to its best advantage. What makes a cut beautiful varies by type, though there are common grounds such as symmetry and proportion. Valentin Magro only uses GIA certified diamonds for jewelry, allowing our clients to be certain of their diamonds’ cut quality.
Diamonds are admired for their brilliance and luster, as well as their symbolism of romance and enduring love. They are also famed for their unparalleled hardness, which makes them resistant to abrasions. Though it’s less apparent than aesthetics, durability is a crucial component to gemstones, allowing them to be worn without falling apart.
Gemstone durability falls under three categories. The first is hardness, or the ability to resist scratches. The Mohs Scale of Mineral Hardness measures a stone’s endurance on a range of 1 to 10, or softest to hardest. With a rating of ten, diamonds are peerless. However, they are still vulnerable to abrasions from other diamonds. A person with diamond jewelry should take care to ensure that their pieces don’t rub against one another, increasing the risk of scratches.
Toughness is a gemstone’s ability to withstand damage from impact, such as when a hand wearing a diamond ring bangs against a table. This quality is measured along a fracture toughness scale. For diamonds, their toughness is between five thousand to eight thousand, depending on the angle of the jewel. By comparison, sapphires are six hundred on the scale, while nephrite is 225,000. To make sure your diamond remains safe, make sure its thinnest portions, such as corners and the girdle, are mounted in secure settings.
Stability determines a jewel’s endurance from temperature, chemicals and light. Diamonds are very stable under bright lights, their colors unchanging even after prolonged exposure. They’re resistant to changes in humidity, acids and most other chemicals. The precious metal they’re mounted on may not be as strong. Gold may sustain damage when exposed to chlorine, such as with swimming pools.
In terms of temperature changes, diamonds are less sturdy. Sudden differences in heat may impact the jewel on a molecular level, causing some parts of the stone to move faster with than others, which in turn may lead to fractures. Thermal shock, or cracks caused by exposure to high temperatures followed by intense cold, may be the most drastic expression of this phenomenon. To protect your diamonds, you may want to remove them prior to cooking, and to make sure to store them away from heat sources.
Cleavage and Chips
Diamonds are made of carbon atoms linked together in a shape resembling two pyramids connected to the same square base. These atoms sit close together, adding strength to the crystal. Their bonds are stronger in some directions than with others. The directions where the atoms are farther apart allows diamonds to be broken if enough force is applied, known as cleavage planes.
Diamond’s cleavage planes lay parallel to their outer triangles. Before the advent of the diamond saw, cutters used them to divide rough, creating multiple finished jewels from a single stone. They also create a challenge when planning the cut of a diamond, as cutters don’t want to accidentally chip a jewel they’re faceting. Planning a cut is easier when the shape is a clear octahedron, but trickier when the shape of the rough is less apparent.
Diamond crystals are also fragile where they are at their thinnest. Vulnerable locations on finished diamonds include overly thin girdles, corners and points at the bottom of the stone. Impacts on these areas may cause cracks, chips and other unwanted effects on the jewel. Diamond cutters usually fashion gemstones to reduce the risk of harm, such as faceting the girdle and adding a culet to the bottom of the jewel.
Among the many methods gemologists use to identify diamonds is by evaluating how they break. When a diamond chips, it leaves curved, stepped ridges known as conchoidal fractures. While such marks are useful when it comes to identifying jewels, intact cut diamonds are still ideal.
To keep your diamonds safe, be choosy about their settings. If your stone is a mixed or fancy cut such as a princess or marquise, make sure that the mounts protects the corners, such as V shaped prongs or a bezel setting. Try to inspect your jewelry every so often to determine if the settings are secure or have loosened. When wearing or storing your pieces, make sure they don’t rub against other jewelry. With proper care, your diamonds will remain pristine for years to come.