Orange diamonds have been called Fire Diamonds for their colour and depth of the hues. Orange diamonds have many colour combinations and intensities from the pure colour fancy vivid orange to a deep brown, almost chocolate orange hue.

Orange diamonds are some of the rarest diamonds available, even rarer than colourless gemstones and their price reflects the rarity. It is hard to be accurate about such unique stones, but many gemologists suggest that orange is the fourth rarest coloured diamond after red, violet and pink.

In this article, we look at where orange diamonds come from, why they are so pricey and how you can enjoy the beauty of an orange diamond at a lower cost than might be expected from their rarity.

What Is An Orange Diamond?

Most natural diamonds are clear or carry a slight yellow tint. Coloured diamonds are usually coloured by traces of impurities that become part of the crystal lattice of the gem. Orange diamonds take their colour from traces of nitrogen in the diamond's structure. The depth of the orange colour is a result of the concentration of the nitrogen atoms. Orange coloured diamonds are not the rarest of fancy coloured diamonds. Most orange stones have traces of other colours modifying the colour. A diamond that has no secondary hue is very rare indeed.

Figure 1. GIA colour grades for orange diamonds. Adapted from https://www.asteriadiamonds.com/media/magpleasure/mpblog/upload/7/2/72739c864483596bd1e077ff7edc950c.jpg

Most orange diamonds are small. The largest known pure orange diamond is 14.82 carats weight; before this diamond was mined the largest fancy vivid orange diamonds were all less than 6 carats. The GIA rarely grades polished diamonds that are larger than 4 carats.

Pure orange diamonds are often called 'pumpkin diamonds'. 'Orangy' diamonds are those where the orange colour is the secondary hue at less than 25% saturation. The primary colour is often pink, yellow, brown and very occasionally red.

Where Do Orange Diamonds Come from?

Most orange diamonds are mined in South Africa or at the Argyle Mine in Western Australia. The latter is famed for its pink diamonds and is the reason why pink and orange colours are found mixed together in a large proportion of orange diamonds.

Treated Orange Diamonds

Because of their rarity and the recent increase in popularity, methods have been devised to create orange diamonds that look like the real thing. These treated or enhanced diamonds can be sold at a much lower price. Annealing, a process of carefully heating diamonds to a very high temperature, can be used to create colours within clear diamonds or to change the colour in an already coloured stone. The diamond is removed from heat when the desired colour change has been attained. While these treatments are generally permanent, exposure to high temperature during jewellery repairs can affect the colour.

An alternative method of treating natural diamonds is to treat them under high pressure and temperature. This is a similar process to that which occurs naturally under the Earth's surface. HPHT does not create pure orange diamonds; they will be a wonderful orange-yellow colour. HPHT treatments are permanent.

The final treatment used to create diamonds that appear to be orange is to coat a diamond with a silica coating. Because the coating is thin and can be scratched, it is not permanent. Silica coatings can also be affected by heat and chemical action.

All forms of treated orange diamonds are much lower in value than the real thing, but they offer a relatively low-cost entry to orange diamond ownership. Buyers should always be informed that a diamond has been treated, but sometimes that does not happen.

If you want to buy a genuine, natural, orange diamond, you must always insist upon having a grading report from a reputable diamond grading lab such as the GIA. A GIA report will disclose if the gem you are considering has been treated to attain its colour or is natural.

Orange Diamond Quality

Coloured diamonds are graded in the same way as colourless diamonds using the industry-standard 4Cs of clarity, cut, colour and carat weight. In the case of coloured diamonds, the colour is the most prominently considered factor. The GIA, the best-regarded diamond grading laboratory grades the colour factor using a scale running from Faint, being the lightest colour to Fancy Deep being the darkest. The colour mix is described using a one, or two-word description. For example, 'Orange' is a pure orange colour and 'Pinkish Orange' is an orange diamond with a secondary colour of pink.

Deeper colours tend to hide inclusions, and so clarity is less critical with coloured diamonds. The rarity of deep coloured orange diamonds means that buyers will compromise on lower-quality diamonds to obtain the vibrant colours they seek.

Cut remains very important as this factor can serve to enhance the colour and minimise poor diamond clarity.

Carat weight is measured as in all other diamonds, but larger stones can be disproportionately expensive due to their extreme rarity.

When buying a natural orange coloured diamond, be prepared to compromise on clarity. Do not compromise on cut quality and be aware that a large diamond will be costly to buy!

How To Make The Best Choice When Buying An Orange Coloured Diamond?

Some buying tips for getting the right orange coloured diamond for you.

1. If you want to buy a natural orange coloured diamond, always insist on a diamond grading report from a reputable diamond grading laboratory such as the GIA.
2. willing to compromise on the clarity grade to buy the colour of diamond that you want.
3. If your budget is tight, then treated diamonds are a budget-friendly approach. You can get a quality diamond with the colour you want at a lower price. Seek out HTHP diamonds for their permanence. The GIA gives grading reports for such diamonds so you can be sure that you have a real diamond and you will know how it was treated to enhance the colour.
4. Choose a setting to enhance the colour of the diamond. A yellow or rose gold setting can make a faint coloured diamond look a little darker.
5. Do not rely wholly upon a grading report before buying. If possible, see the diamond in person, or make sure that you have viewed high-quality pictures and video of the stone.
6. Be realistic about the size of the diamond you buy. Large orange diamonds are scarce and so are much more expensive per carat than smaller stones.