Sapphire and Ruby Cuts
July 25, 2010 / Coloured Gemstones
Sapphires and rubies belong to a gemstone family called corundum, also known as crystalline aluminum oxide. As they both have the same chemical composition, their physical characteristics are very similar. The presence of small amounts of trace elements however creates noticeable differences in colour.
Ruby is red corundum while sapphire can be all the other colours, including blue, green, pink, yellow, orange, purple and others. As they share the same physical characteristics, a similar approach is taken to both when cutting the gemstones.
Perhaps more than any other type of coloured gemstone, rubies and sapphires are often cut to retain as much weight as possible, while still aiming to retain a pleasant shape. Weight is important because rubies and sapphires can command prices in the thousands per carat. Unfortunately this tendency can lead to stones that are disproportionately deep or overly shallow for their girdle size, and therefore lack brilliance due to light not being reflected up through the crown of the cut stone. A well-cut stone should have pleasing proportions, good internal reflection and a symmetrical girdle regardless of the shape.
Both sapphires and rubies are well suited gemstones for jewellery. They are tough stones, right behind diamonds on Moh’s scale of hardness, and are therefore suitable for all types of jewellery, including engagement and wedding rings.