From the soft blush of a fancy colour pink to the icy brilliance of a D-grade white, the hue of a diamond not only determines its look but also its value and meaning. Lab grown or natural diamond, it’s only right to query how steadfast its colour is and whether it’s likely to change.
Does a diamond’s colour fade over time? The short answer is no. Both natural diamonds and laboratory-grown alternatives (LGDs) are generally incredibly stable when it comes to colour. That said, there are a few exceptions. Read on to discover more…
What “colour stability” means for diamond clarity and colour
Colour stability in a diamond refers to how well it retains its colour. As a rule, a diamond’s shade is baked into its atomic structure and even after it’s been cut and polished, its colour stays the same for life.
Certain types of lighting, different coloured metals surrounding a diamond, and even dirt and grime can make a diamond’s colour appear to have changed. For instance, if a diamond is set in yellow gold, the warmth of the gold can accord a more golden tone to the diamond. If you wear a diamond ring every day, lotions and creams may make the gemstone appear slightly cloudy, and affect diamond clarity and colour, if only for a little while. But view your diamond in different light, have it re-set or take it for a professional clean, and you’ll quickly breathe a sigh of relief.
Both natural diamonds and LGDs are highly stable when it comes to colour, but let’s go deeper and really compare.
Natural diamonds: formation and long-term colour stability
Do you know how natural diamonds are formed? Around 4.5 billion years ago, stardust from the galaxy accumulated in the core of the Earth. It was this source of carbon that, when bonded under intense heat and pressure hundreds of kilometres deep, then crystallised and formed diamonds.
How natural diamonds reach the surface
These incredible gemstones were then brought to the planet’s surface by powerful volcanic eruptions millions of years ago and became lodged in pipe-like rocks. Even today, most are buried far too deep for us to recover.
Why natural diamonds resist change over time
Because natural diamonds are formed almost entirely from carbon atoms bonded together in a rigid tetrahedral structure, they are not only the hardest naturally occurring substance on Earth1 but also one of the most stable2.
How natural diamonds get their colour
The small amount of trace elements (such as nitrogen) or stress-induced irregularity in a diamond’s structure that causes its colouration is locked into place under normal conditions, making it highly resistant to change. Generally, it would take extreme conditions (such as very high temperatures) to change the colours of a natural diamond.
Chameleon diamonds and their rare, temporary colour shifts
But there are some exceptions, however. A ‘chameleon diamond’, a very rare type of natural diamond, is typically a grey-yellow-green colour. However, when it’s heated to over 300°F (148.88°C) or exposed to light after a prolonged period in the dark, it changes to yellow. This colour change typically lasts around 15 minutes although some chameleon diamonds emit a yellow glow (or phosphoresce) for up to an hour3. Cool, right?
Pink and Argyle diamonds’ response to light and heat
Then there’s the mind-blowing science behind pink diamonds, particularly the coveted Argyle ones. These diamonds are photochromic, meaning their colour can fade under UV light and reappear under visible or blue light. They are also thermochromic. Expose them to temperatures above a scorching 1,472°F (800°C) and their colour will take on a more purplish tone4. Also very cool.
The science of colour grading diamonds
Colour is one of the 4Cs of diamonds. The diamond colour scale is used to assess and certify diamond clarity and colour (or, technically, the absence of colour). For white diamonds, colour is graded on an alphabetic scale from D to Z, starting at completely colourless gems and ranging all the way to those with a noticeable warm, yellowish tint. A diamond with any shade or depth of colour beyond that is called a fancy colour diamond – think vivid reds, pinks, blues, greens and browns, for example. Fancy coloured natural diamonds are graded using a separate system that’s based on hue, tone and saturation.
Why a diamond’s colour grade stays consistent
Because diamond colour doesn’t change over time, once your diamond has been given its colour grade, you can rest assured that it’ll stay that grade for life.
Lab-grown diamonds: production and colour stability
Their name would suggest that lab-grown diamonds (LGDs) are meticulously created in sterile laboratories but, in most cases, they’re produced in huge industrial manufacturing plants.
How lab-grown diamonds are created
While LGDs have the same chemical and optical properties as natural diamonds, they’re created in an artificial environment in a significantly shorter timeframe.
The two common lab diamond production methods: HPHT and CVD
Generally, there are two different methods of producing LGDs. One is High-Pressure, High-Temperature (HPHT), which attempts to recreate the extreme geological conditions required for natural diamonds to grow deep in the Earth, in a factory using powerful high-pressure presses.
The second technique is Chemical Vapour Deposition (CVD). This method involves heating carbon-bearing gases, such as methane, to extremely high temperatures in a vacuum chamber. The process breaks up the carbon-bearing molecules, allowing the carbon atoms to gradually build up layer by layer.
How stable is colour in lab-grown diamonds?
Regardless of method, LGDs are generally as colour stable as natural diamonds, since both types have stable atomic structures5. However, a subset of CVD pink-grey diamonds with high silicon content can behave a little differently. Much like Argyle pinks, these gems are subject to photochromic responses, shifting to a cooler, bluish tone when exposed to UV light.
Colour treatments: what to check on reports
It’s also worth noting that many CVD diamonds undergo HPHT post-growth treatment to remove brown hues, or irradiation and heating to create vivid fancy colours like pink, blue, or green. These treatments are permanent and can also be carried out on natural diamonds, so color origin testing is wise6.
Insist on transparent disclosure of such colour treatments, so you’re well aware of the colour stability of the diamond of your choice. Ask if the colour is natural, treated, or growth related, and whether the report states it.
Can diamonds change colour over time?
No, under everyday conditions, diamonds don’t change colour. But, as we mentioned, sometimes they can appear to have changed colour due to external factors. These could include:
- A build-up of oils, lotions, grime or dust pollution that makes a white diamond appear dull, cloudy, or discoloured.
- Lighting changes that shift how a diamond reflects colour or how the light travels through it.
- Having a diamond re-set in a different coloured metal. For example, a colourless diamond may appear creamier or yellow-tinted when set in yellow gold. Stick to silver, platinum or white metal settings if you want it to remain icy in colour.
- Certain diamond treatments or coatings that fade or wear off over time, though this is rare with high-quality gems from trusted sources. Again, check the origin of a diamond’s colour before buying.
If you’re thinking: “why does my diamond look cloudy?”, most often it just needs a good cleaning.
Why colour stability still matters
Besides the few exceptions we’ve flagged, you can be reassured that your beautiful natural diamond won’t unexpectedly change colour over time (even if, in very rare cases described above, it does shift temporarily after you have had a manicure, or you have been soaking up some rays on the beach).
Fancy coloured natural diamond or not, your gemstone of choice should absolutely stand the test of time in terms of both its dazzle and colour.
Instead of worrying whether a diamond will retain its colour in the years to come, focus your attention on finding one that fits your own unique style and story. When you do find it, be sure to show it plenty of TLC.
Sources
- www.pursuit.unimelb.edu.au/articles/diamonds-the-hard-facts/ ↩︎
- www.wtamu.edu/~cbaird/sq/2013/12/17/why-do-diamonds-last-forever/ ↩︎
- www.4cs.gia.edu/en-us/blog/colored-diamonds-mysterious-chameleon-diamonds/ ↩︎
- www.fcresearch.org/chromism-in-pink-diamonds-3/ ↩︎
- www.revediamonds.com/blog/do-lab-grown-diamonds-change-colour-over-time/ ↩︎
- www.gia.edu/gems-gemology/fall-2014-labnotes-irradiated-cvd-synthetic-diamond/ ↩︎
