Bi-Colour Sapphires

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Bi-coloured or two-tone sapphires are among a rarer variety of corundum gemstones, which are valued for a variety of reasons: from their notably distinct dual colour tones to the kind of colour combinations in which these gemstones are found in. The bi-coloured sapphires are gemstones stone that contains two colours, which forms as a result of colour zoning combined with the particular combination of elements that are present in the gemstone. Bi-coloured sapphires command a unique demand in the market for a gemstone type which is generally understood to contain only a primary colour, that is spread, for the most part uniformly throughout the gemstone, with slight variances in shades and tone depending on the gemstone in question. With this bi-colour variant, however, the presence of dual or two tones makes it a standout variety.

How Bi-Coloured Sapphires Emerge: The Role of Color Zoning

Colour zoning is a key facet in sapphires, and especially so in the two-toned variety, since the colours are not always uniformly present throughout. In cut gemstones, the process that led to its specific cut was partly, if not primarily is determined by the presence of colour in the rough stone from which it was shaped from. With factors like the type of hue, its concentration and zoning playing a role. In bi-coloured sapphires, colour zoning is an important factor owing to the fact that there are two colours at work and the quality of both need to be factored in. The type of the two hues, their location in the gemstone, and how they contrast (or complement) one another, combine to determine the value of the gemstone. When it comes to sapphires, colour is a consequence of the presence of external elements like titanium, iron; and the combination of these elements gives the gemstone its variety of colours: blue, pink, yellow. However in the two-toned variant colour is a consequence of the presence of these elements which are concentrated in specific regions, in a specific way within the stone.

What Bi-Coloured Sapphires are Not:

Sapphires come in a wide range of colours. Most of us are aware of the famous blue, and the now increasingly popular pink, yellow, and white variants. In addition to those which contain distinct colours, certain sapphires in their natural mineral form are found in states where they contain one or more colours. The concern here is the two-toned variety, which as the name suggests are stones that contain two hues found within the same stone. The quality of the two-tonnes that are present within the stone is often determined by its cut, in addition to the presence of various colours, and their intensity within an uncut gemstone. Which are not always uniform, thus requiring the skill and intent of the cutter. So here are three factors you need to keep in mind when it comes to correctly identify what a bi-coloured sapphire:

Sapphires with More than Two Distinct Colors

As noted the key determinant in bi-coloured sapphire is the presence of two colours, not one, not three, but two. Two is a key factor since it not just the presence of dual colour tones, but how these colours are present within the stone. A key factor when it comes to two-toned sapphire variants is the role of contrasts. Contrast is a key phenomenon that emerges in the presence of two factors that are different in ore more ways but are yet united by certain commonality. In two-toned sapphires, the colours whilst different are united in that they are present in the same stone. And it is the contrast between the two colours that determines it character.

Bi-Coloured Sapphires are Not Parti Sapphires

Parti sapphires or polychrome sapphires are gemstones that contain more than one colour, often found in yellow and green hue combinations, but the key difference lies in how the colour is spread throughout the gemstone. Unlike two-toned sapphires, parti sapphires (which fall under the category of multi-coloured gemstones) are corundum crystals where the colours, two or more, are present in various parts of the gemstone. Often spread across, randomly in the gemstone, features which are accentuated by the cut of the gemstone.

Sapphires with a Single Colour

This should be a no-brainer, bi-coloured sapphire is determined by the presence of two colours, not one. However, in certain single coloured sapphires, the type of colour zoning might create the impression of two colours. However, in reality, these are gemstone with a single colour, but the strength of the hue is not uniformly spread across the gemstone.

Countries of Origin for Bi-Coloured Sapphires

The top sources of sapphire are countries like Myanmar, Australia Ceylon (Sri Lanka), Thailand and more recently with the rise of the United States, we have Montana sapphires. The best quality sapphires are those that originate from countries like Thailand, Myanmar and Ceylon (Sri Lanka). Ceylon sapphires are valued for both their beautiful hues unique colour variations. Australia's parti sapphires at times are confused with bi-coloured sapphires, but this is not correct. Whilst certain parti sapphire may have two colours, the presence of these colours do not reflect the two-tonne sapphire’s character.

Identifying a High-Value Bi-Coloured Sapphire

This is an interesting question. Since bi-coloured, as noted are valued for their relative rarity. However, their value is determined by the quality of the two tones that are present in the gemstone. Sometimes the two colours that are present in the gemstone are not uniform, with colours dotted across the gemstone, or with certain areas containing a greater concentration of a single colour. In bi-coloured sapphires, the presence of two colours that are able to produce contrasting effects command the greatest appeal and hence value. This in turn is a feature of the kind of colours that are present in the gemstone. This takes us to the importance of the complementary character of the colours.

Colour Complements and Colour Division

Top-quality bi-coloured sapphires contain colours that exhibit a division of colour that are distinct and clearly discernable to the naked eye. The most important aspects when evaluating a top-quality bi-coloured Sapphire are the intensity of the colours, and how two colours are present together but apart in the same gemstone, whilst the clarity of the gemstone remains unaffected. In addition to the presence and prominence of colour division in the gemstone, a key factor that separates a quality bi-coloured sapphire from the lower grade is the type of colours that are present in the stone. Gem experts, like colour scientists, understand the workings of colour: in terms of how they appear under different lighting conditions, and the effects they produce in relation to the presence of other colours. Quality two-toned sapphires are those which not only contain a stronger colour that is clearly divided, without random zoning in the gemstone but a stone that contains colours that are complementary in character. For example, a two-toned sapphire that contains red and pink are a great example, provided other factors are well placed. On the other a sapphire with yellow and blue, or green is not likely to be a great match, even if it scores well in other areas of gem colours, in addition to the 6Cs. Parti sapphires are notable in this regard, since the most famous ones, like the Australian parti sapphire.