Anyone who meets me finds out sooner or later how enthusiastic I am about gemstones – usually sooner. I’m writing a few blog posts for ACJ Wessex, and I’ll be talking about gemstones quite a bit, but also about jewellery, contemporary jewellery, jewellery materials… This time I’m talking about the wonderful colours of sapphires and garnets. Mostly, with a few digressions…
We tend to think of garnets as dull, blood red stones, and sapphires as blue gems, whether that’s the cornflower blues found in Kashmir or Sri Lanka, or the darker blues often associated with Australian mines. However, both stones come in a rainbow of different colours.
Let’s start with sapphires. Look at this gorgeous ring by Georgina Ettridge, for example, which features a lovely green sapphire. I think it works really well with her leafy, woodland vibe.
Or check out this beautiful ‘Fire and Ice’ pendant by Gill Mallet, which includes fiery yellow sapphires.
‘Pure’ sapphire is actually colourless and is sometimes used as a rather unsatisfactory substitute for diamonds – it just doesn’t sparkle enough to do that job. For those who are interested – sapphire is a compound of aluminium and oxygen, Al2O3, called corundum.
The colour in sapphires comes from impurities – but these impurities give us rich blues, vibrant pinks, forest greens and more subtle mauves, peaches and browns, so thank goodness for them! One of the most desirable colours for sapphire is padparadscha, which is pinky-orange. Or orangey-pink. Either way, most of us can’t afford one. The only colour that sapphire can’t be, is red, and that’s because if it was red, it would be a ruby. (Did you know that rubies actually do glow a little bit? But that’s a digression for another blog post … watch this space).
As sapphire crystals grow, there can be different impurities available, so sometimes they come out with different colour zones. Traditionally, fine jewellers prefer pure, deep, single-coloured sapphires, but contemporary jewellers love to play with the design possibilities offered by colour variations. Just look at this amazing sapphire slice.
It comes from Zylana Pearls and Gemstones , who has a great IG feed of special stones. I have been having lots of fun playing with ideas for a special gift to myself with this stone at the centre. I also offer commissions with unusual stones.
Garnets come in bright, vibrant colours as well as more subtle shades. Whereas sapphire green is deep and foresty, garnet green is often bright and can rival or even exceed emerald in its greenness. It can be minty or grassy or like spring leaves as they unfurl in the sunshine. Check out Gill Mallet’s earrings here. Garnets also come in reds and oranges and yellows like fire, and an intense purple, as well as the more well-known blood reds, pinks and pinkish browns – for example, Lynne Eales’ earrings here.
It is possible to find colourless and black garnets and an iridescent rainbow garnet. Blue garnets are much rarer, but they do exist. I have a garnet which is blue in daylight, but in candlelight goes deep red. Gorgeous! Here are just a few of my garnets – on the left are two mauvish – brownish colour change garnets, a deep red-orange spessartine, an orange spessartine, a greenish yellow mali garnet, two orangy brown malaya garnets and a wonderful deep purple garnet from Kenya. Most of these came from Marcus McCallum, and some from Ward Gemstones.
Garnets are actually a complex series of minerals which have similar structures. It is not necessary to know about the chemistry of garnets to enjoy the stones or the jewellery – but I find it fascinating! For those who are interested, they all have this structure: X3Y2(SiO4)3 – so you might get Fe3Al2(SiO4)3 (almandine) or Ca3Al2(SiO4)3 (grossular, including tsavorite), or Ca3Fe2(SiO4)3 (andradite, including demantoid).
Unlike sapphires, garnets are not naturally colourless. It is the elements which make up their basic structure which are responsible for the colour rather than impurities. So, in almandine garnets, it is iron which creates the pink-red-brown colours, and these colours can look a bit like blood, because it is iron that gives our blood its colour. By contrast, pyrope garnets contain magnesium and, although they can be quite dark, they can also be a wonderful, bright red. Spessartine garnets contain manganese, which can lead to bright oranges, pinkish orange almost like padparadscha sapphires, and a range of pink-orange-browns. Check out the spessartine garnet in Candied Silver’s opal and garnet ring, pictured above.
The presence of calcium contributes to the vibrant greens of tsavorite and demantoid garnets, and then there is my absolute favourite, uvarovite, which contains calcium and chromium. It only grows into very small crystals, so it is usually found in drusy, like these little trees, which one day I am going to decorate and make into magnificent seasonal earrings.
Finally – with all this variety, why do we think of garnets as dull red and sapphires as blue? Well, it’s mostly a matter of history. For a long time, the most common known garnets were small reddish crystals that looked like pomegranate stones – hence the name. The more exciting colours have mostly been mined only since the 1960s. Even more than this, before modern analytical techniques were available, stones were classified by their colour. Red stones were rubies (and interestingly, some of the most famous rubies are not, in fact rubies, but spinels – I digress again!) and blue stones were sapphires, even if they were in fact lapis lazuli. We may now have electron scanning microscopes and Raman spectroscopy to analyse the structure of different stones which look the same, but our cultural understanding has deep roots in the past, so it is changing more slowly than our scientific understanding of stones.