Characteristics of Rubies

_{Ruby Gemstone Rectangular Cut from Brilliyond}

Rubies make up the top three precious gemstones group in the world. When considering the character of rubies the most standout feature is its colour. ‘Rubies are red’ is a saying that has come to a part of our vernacular. And with good reason, the colour is arguably the most significant feature, for it is the colour that sets rubies apart from their equally prominent cousins. When learning about the characteristics of rubies the attention revolves around the factors that determine the origins and distinguishing features of this stone. For it is important to note that ruby stones are not the only gemstones that are renowned for the colour red. So the question is what sets rubies apart, in answering this we shall provide a quick overview of the characteristics of rubies.

Geological Origins of Rubies

Rubies are corundum crystals, that consist of aluminium and oxygen atoms (Al₂O₃). As an aluminium oxide mineral, in their pure state, corundum crystals are colourless, with the colour that is present in the gemstone resulting from the presence of chromium, a relatively rare trace element. What makes rubies specials is their formation: the addition of chromium atoms to the aluminium oxide mineral is not a simple or likely process. For deep within the Earth’s surface where corundum based gemstones are formed, the chances for corundum to incorporate levels of the trace chromium whilst ensuring that no other elements contaminate the mineral, notably highly abundant elements like silica and iron. This is what makes rubies special, as their ability to avoid the addition of elements like iron, which are present in sapphires, and contribute to their colour, and connect with the rare chromium.

Mineral Character of Rubies

What Gives Rubies their Colour

Rubies, as noted is a member of the corundum mineral species that includes sapphire. Rubies are valued for rarity and their colour. As a distinct category in the world of precious stones rubies gained their recognition by becoming the gemstone representatives of the colour red. The blue, white (colourless), green and purple took up by sapphires, diamonds, emeralds and amethysts. Since the mineral corundum in its pure form is colourless; the highly valued colour in the gemstone emerges as a result of trace elements that enter the mineral, and become a part of its crystal structure. The science that underlies it is rather complex, but essentially involves the substitution of aluminium ions with that of chromium, which in turn affects the stone’s ability to interact with light. And this is the central factor in determining the colour of gemstones. How they interact with light rays. When it comes to ruby quality, besides the absence of inclusions, and other blemishes, the greater the level of chromium, the stronger it's colour. This is why rubies from countries like Burma, and in recent times from Mozambique are most popular, owing to their strong red colour that is devoid of other shadings.

Rubies vs Sapphires

Rubies and sapphires are both made of the same mineral corundum: that consist of alumina and oxygen atoms. The difference lies in their colour, which in turn is a reflection of the trace mineral character of the gemstone. With rubies being red, and sapphire being blue, and a number of other colours and tones. Besides their colour, rubies differ from sapphires in that they are gemstones of the same corundum family that are identified by a designated title. On the other hand, corundum crystals that are not blue and not red are not given a designated title. The key difference between sapphires and rubies is that rubies are exceptionally rare. As members of the corundum family, rubies are a specific type of corundum crystal.

Natural vs Lab Grown Rubies

Natural rubies form within the Earth’s surface, formed from corundum crystals, consisting of aluminium oxide. Once mined rubies are taken by jewellers and gem merchants who, cut, often treat and polish the gemstone. Natural rubies owing to their rarity expensive and often difficult to come by at competitive prices. And when combined with the prevalence of rubies that carry inclusions, has in turn given rise to the demand for synthetic or lab-grown rubies, as a way to overcome this limitation.

The origins of lab grown rubies can be traced back to the year 1877, when the chemist Edmond Fremy developed a method for ruby manufacturing using molten baths of aluminium oxide, yielding the first gemstone quality rubies. The highly popular Verneuil method was developed by Parisian chemist Auguste Verneuil, who worked in collaboration with Fremy. Which involved the use of flame fusion. Verneuil announce his work in 1902, and published details in 1904. The Verneuil process begins with the melting of pure aluminium oxide into the Verneuil furnace. If one wishes to understand the process of how rubies are grown in the lab, it starts with powdered aluminium oxide, which is subjected to oxygen, that is supplied, along with alumina. This combination is then subjected to hydrogen, and then comes the addition of various levels of trace elements. In the case of rubies, it is chromium that makes the difference in producing the desirable red colour.

When it comes to determining the value between natural lab grown rubies, perception is key. Most people still greatly prefer natural rubies over synthetic variants owing to their rarity and the desire to own a naturally formed precious stone. Whilst lab grown rubies are becoming more popular due to the ethical and environmental concerns that surround them. However the dominance of natural ruby stones is indirectly strengthened by the growing focus on ethical mining, and efforts directed at environmental protection.

Rubies vs Red Gemstone Substitutes

When it comes to the world of red coloured gemstones, rubies aren’t the only kids on the block. Whilst the idea of a valuable red gemstone is instinctively associated with rubies, there are a number of competitors. Notably, we have garnets, red spinels and Rubellite (red tourmaline). Here we will break down each of these red gemstone types and how they contrast with the famous rubies, and what you need to consider when choosing between these alternatives.

Red Garnets

Garnets are a group of minerals that are found in a number of sub-variants and hence come in a number of colours. They range from red, green, yellow, orange and even black. When it comes to the colour red, whilst rhodolite is arguably the most popular garnet variant. Interestingly since red garnets come in a number of mineral variants in the garnet variety, and as a result, the features of the garnet in terms of the basic characteristics also vary from others. Here we will compare rubies with the almandine type of red garnets.

Red Spinel

Red spinels are a part of the spinel group of minerals, that consists primarily of the magnesium aluminium oxide variant. Spinels like rubies are naturally colourless and get their various hues from the various elemental impurities that enter them. For a long time confused with rubies, spinels are strong competitors to rubies, with certain high-quality red spinel variants being comparable to rubies. Spinels come in a number of variants, in terms of colours; with ruby-spinel being the most interesting one, owing to its similarity with rubies.

Rubellite (Red Tourmaline)

Tourmalines are considered to be among the most colourful gemstones in the world and come in a variety of colours, including multicoloured tourmaline stones. Rubellite is a variant in the tourmaline family, considered an accessory mineral that is found predominately in parts of Brazil, with its name derived from Latin for the colour red. Rubellites it may interest you are rarer than rubies, for the red variant of this gemstone is not easy to come by in nature.

In sum, there is no easy choice. Rubies remain the safer option when it comes to going for red gemstones. But when considering the price, colour tone (i.e. lighter more transparent shade), then other red gemstones do enter the mix. Further, if one wishes to go one up on the ruby then rarer variant from these other gemstones types may be the way to go.