The King of Gemstones. Rubies are highly sought after and can command the highest prices of any coloured gemstones. Like sapphires, rubies are a type of corundum, the only difference being the presence of chromium which gives them their red hue. They have good durability with a hardness of 9 on the Mohs Scale, making them an excellent choice for jewellery. Due to their rarity, Ruby prices have been increasing significantly in recent years, making them an excellent investment piece.
Colour - This is the most significant quality factor in determining a ruby’s value. The highest quality rubies are a bright but deep vivid red colour without too much orange, purple or pink tones. Often the term ‘pigeon’s blood’ is used to describe the colour of a top quality ruby. Colour saturation is important. Colour must be evenly distributed and not considered too dark or light. Slight differences in colour can make significant differences in the value of a ruby.
Clarity - Top colour rubies that also boast excellent clarity are rare and considered extremely rare and highly valuable. It is generally accepted that most rubies have some inclusions that can be seen with the eye or under a 10x jeweller’s loupe. Inclusions will normally be in the form of long mineral deposits called ‘needles’ or fine needles called ‘silk’.
They may often have included mineral crystals, ‘colour banding’ where darker lines might be evident in the stone, ‘colour zoning’ where saturation of colour varies and ‘healed breaks’ that look a little bit like fingerprints. Extremely bad inclusions will lower a ruby’s value, especially if they can impact the durability of the stone.
Cut - As with all gemstones, the crystal shape and shape of rough determines a stone’s final shape. The most common shapes for rubies are ovals and cushions, due to the crystal structure. Round, octagonal, pear or marquise shaped rubies are available but are often rare in larger size stones of good quality. Rubies are cut to achieve the best possible colour, proportions and weight retention. What sets Caldera apart from many other traders is our strong focus on exceptionally well-cut gemstones. Choosing a well cut gemstone is as much an art as a science. It is an area that we pride ourselves in and we excel in.
Weight - The per-carat price of ruby increases dramatically as size increases, especially for better-quality stones. Fine quality rubies over one carat are very rare but prices for a two or three carat ruby can often be more than double or triple the one carat price.