Ruby and Diamond Ring. A bright pinkish ruby weighing approximately 0.40 carats sits at the centre of this beautiful cluster ring. Rubies, like emeralds, owe their colour to the element chromium, but the difference in their molecular structure results in a spectrum of pinks, purples and reds. With their combination of beauty and rarity, it’s not surprise that rubies are often known as the ‘king of coloured stones’, and historically are the most valuable coloured stone per carat. This oval stone’s outline is echoed by its setting, encircled by early 20th century cushion-shaped diamonds, in a millegrain-bordered mount that sits low on the finger. A beautiful example of a classic design, an excellent choice for an engagement ring.