The Perfect Purple: Hunting for the Right Hue

Purple is definitely the gemstone color of the year! Although it’s not just one color… I’ve received requests for specific hues in the purple family: lavender, lilac, magenta, periwinkle, deep purple, blue-purple, fuchsia. We are inventing new names for our listings at this point to distinguish the shades. How come there are so many types of purple, sometimes in just one gem, i.e. sapphire or spinel?

The purple spectrum in gemstones is very wide because there are so many trace elements that make up its color: iron, titanium, vanadium and chromium all contribute to the purple spectrum in both sapphires and spinels. On the other hand, red in corundum (sapphire, ruby) is only caused by chromium.

When people ask for a specific shade of purple to be matched, it is a near impossibility to find the right shade. Matching a gem to a photo already creates a problem as a photo of a gem never really looks like the gem it represents. Just recently I sent photos of a box with about 10 different shades of dark blueish purple sapphire to a client in Australia to pick which shade matched the earring she lost. I sent the photo under daylight and LED light so she could see how the light was affecting the color as well. I never heard back. Too many shades of purple is what I surmised and expected. The nuances of even the dark blue-purple spectrum are too varied to make sense of it when matching a photo to the remaining half of a lost earring.

Another relevant point is that matching gems from two different locations rarely succeeds because the trace elements in the locations will differ. For example, Madagascar purples are more often softer and more medium purple to reddish purple, whereas Sri Lankan purples tend to be darker and more blueish on average. So while there is overlap with some of the shades, it may not be enough overlap for the gems to really match if seen side by side.

By difference in location I don’t mean just different countries, by the way. To see geological variation, you only need a few meters of space, not a few thousand miles. When you are exploring a pocket of gems in one area in a tunnel, you will already find some color variation.

Also, if the gems are mined by washing a layer of sediment from an old river bed either on the surface or a few meters underneath, you can expect to find even more color variation. Why? Because the runoff from mountainsides and hills that has collected in the riverbed could be from far away and will be all mixed together.

I recently received a request for a specific light blueish purple set of 3 matched round sapphires, 4mm-6mm. From the photo I was assuming that the tone the client was after was Sri Lankan and roughly matched a shade that I have seen at shows until maybe 2020 or 2021. I asked about origin of the gem in the photo she sent me, so I could determine whom to call to get the color. I also asked about treatment and when the photo was taken. This information turned out to be unavailable, and since that hue was most likely a few years old I couldn’t track it down. I face a similar problem when matching greens in tourmalines (not pure chrome colored green, but all the other greens colored by mixes of iron, vanadium, copper). Blues in sapphires or blues in spinels are much easier.

I am also regularly asked for sapphire melee (say 1mm-2mm) that’s deep purple. This means I have to find vendors who still carry older Sri Lankan material as the Madagascar sapphire rough is not saturated enough to cut melee that small that’s still purple – it turns into a faint lavender color. Pinks are much easier to find in that size, even saturated pinks (i.e. Burma ruby, Mozambique pink sapphire), but along the more mid purple to blue purple range the saturated tone is almost non-existent.

So as a buyer, if you have a very specific color shade request, what do you need to do in order to get it filled? Here are a few pointers.

1. Origin affects color hues, so try to find out where the gem you are matching is from.
2. Treatment affects color. You need to know if the color is a treated color or occurs naturally, and what treatment brought it about (if any). For example, bright orange or reddish orange tones in sapphire are achieved by diffusion with beryllium. If you want the beryllium color/shade, you have to let your vendor know that that’s the color you are after, because it doesn’t naturally occur so you’d immediately be told that it can’t be found. So don’t point to a beryllium orange and say you want a natural stone. We are gem sellers, not genies. Miracles happen elsewhere.
3. Photos are inaccurate, so don’t expect a photo of a gem to match to an actual gem when you see the gem and the photo side by side. If you have to send a photo instead of providing a description – yes we gem sellers often go by description, not photo – then add the description to it or give us an actual link to a gem you are matching so we can do some research to find out more about it. It can also matter at which color temperature the photo was taken. Color temperature is affected by the latitude of the place where the photo was taken, the time of day and the equipment used. Cameras often have blue tints, which is fixed by adjusting the white balance, but not everyone does that. And of course, you do not know if someone did or not.
4. The hues in gem finds change over time. Therefore, we need to know when the shade you are matching was most commonly seen (online, at shows, or on location). As I go to trade shows at least 3x a year, I can see the shades drift over time. Having a reference point about when that shade occurred or seemed to be circulating in the market helps me figure out who might still have it. No vendor carries everything, and many gem dealers have connections to some locations and not others. I’m not going to ask a Madagascan sapphire dealer for periwinkle for instance, as that would make no sense. The trace element composition in Madagascar tends towards more reddish tones of purple, not towards blues.

And finally, if you do have an actual gem you want to match, then using it as a color comparison is ideal, so bring it to the viewing or the show, or even send it to the vendor you are working with to find a match or something similar.

Happy color matching!