The Mineral That Painted The World Blue It’s no secret that humans love to make art.

But to make good art, you need good supplies. A sculptor needs clay, a musician needs an instrument, and a painter needs paints.

For as long as we’ve been painting the town red, or green, or aquamarine, we’ve needed to find the  best pigments for the job. Which is where this striking mineral called azurite comes in. For thousands of years, people all over the world have used this pretty blue rock to make pretty blue art.

But the biggest mystery surrounding azurite has been why one group in particular… didn’t. [intro] Azurite is a naturally occurring copper carbonate mineral that tends to form near the top of copper ore deposits, when the metal-rich rock becomes weathered and oxidized. If you’ve ever seen a copper penny in your home turn a kind of bluish-green when it’s exposed to the elements for too long, it’s basically that. Azurite is named for azure, which just means blue in a bunch of languages.

And when it’s crushed, it turns into a blue powder that people quickly realized can be used as a pigment. It’s even been called the most important blue pigment in medieval European art. If you know anything about art from this period, you might think of the blues as coming from ultramarine, not azurite.

Ultramarine is made from the mineral lapis lazuli, and it has also been a popular blue hue for centuries. But there’s not a ton of lapis lazuli in Europe, so ultramarine was ultra-expensive. However, Europeans did have plenty of azurite from deposits in modern-day Slovakia, France, Hungary and Sardinia, making it much cheaper than ultramarine.

So for artists on a budget, it became the natural choice. And these artists even came up with a clever trick to stretch their supply of ultramarine further, using azurite. They’d apply the azurite as an underpaint and then paint just the  top layer with ultramarine, meaning you’d need less of the pricey stuff to cover your canvas.

But there’s one small problem. Over time, azurite can react with water molecules in the air, which causes the azurite to lose some of the carbonate in the crystal. And that reaction turns it into a green-colored copper mineral called malachite.

Azurite and malachite are chemically very similar, but malachite is more stable. Which means that under certain conditions, azurite can just turn into malachite. So, it’s common to find  parts of medieval paintings that were once bright blue, but now are a muddy greenish color, which was probably not what the original artists intended.

While azurite’s blue-green color shift may have been unintentional, other artists around the world found ways of manipulating the pigment to choose the kind of blue they got. Take the art from China and Japan, for example. Artists in Asia found that playing with the size of the pigment particles alters its refractive properties, and thus the color of the paint.

For instance, grinding azurite superfine makes it a light blue, whereas coarser particles give a darker shade. And heating it up could help artists achieve an even deeper blue. In some Asian cultures, azurite symbolized longevity and immortality, meaning that paintings might feature huge boulders of azurite in the background.

And when you want to paint a picture with azurite rocks in it, what better color is there than azurite paint? But azurite was a lot rarer in Asia than it was in Europe, which made the paint more expensive. During the Ming dynasty in China, the royal courts ended up devoting a ton of resources to extracting it.

It was even collected as a tax from Chinese provinces, and at one time it was 2000 times more valuable than silver. So when artists would paint  portraits with azurite, they were really showing  off their subjects’ wealth and standing in society. But while we know that a lot of cultures did use azurite pigments in their artwork, there’s one big blue-loving civilization that somehow never turned to azurite.

Or at least, that’s what we thought. The ancient Egyptians used a ton of blue in their art, but their go-to pigment wasn’t a natural one. The pigment known as Egyptian blue was made by heating up scrap copper with sand, lime and soda, which sounds tastier than it was.

And from what we can tell, most of the blue in Egyptian art comes from this man-made pigment. But there’s a mystery. There are plenty of azurite deposits on the Sinai peninsula close to Egypt, and we know the Egyptians mined a lot of their copper from that region.

So scholars have always wondered why Egyptian artists never seemed to use that azurite stash alongside Egyptian blue. And the mystery took more  than a hundred years to solve. See, there was this archaeologist who found a seashell with blue pigment smeared inside it way back in 1895, and he thought the shell was used as a painter’s palette.

He also declared that the pigment in that shell was azurite. However, he never wrote down, like, how he figured that out. So we have no way of knowing if he was right about it being azurite or not, which has led other researchers to be… a little bit skeptical.

And for literally a hundred years, this was the only time any researcher had even suggested that Egyptians used azurite pigment anywhere. It took until the mid-2000s for the presence of azurite to actually be confirmed in Egyptian art. And this time they did write down how they did it.

Specifically, they used a technique called Raman spectroscopy, which analyzes how light is absorbed by a mineral sample. It’s so specific that every mineral’s signature is pretty much unique, like a fingerprint. To be clear, they were not looking at the same artist’s palette identified back in 1895, so still no word on whether that guy was right or not.

But they did definitively show  that their blue pigment specimens were indeed natural azurite and  not artificial Egyptian blue. And that’s not all. While preparing an exhibition  on the the pharaoh Hatshepsut, the Metropolitan Museum in New York analyzed some artifacts from her reign, dating to around 1550 BCE.

Like this mysterious scrap of painted leather that depicts a somewhat, uhh, spicy scene. And while they aren’t totally sure what this leather thing was, their analysis showed that the deep blue paint used in the foliage around the edge was made of azurite. So there are at least these  two examples of azurite being used in Egyptian art.

Huzzah! But researchers still have more questions, like why the mineral was so rarely used, whether it had special significance, and most importantly, whether there’s any more azurite in Egyptian art that they haven’t found yet. In any case, we do know that this lovely blue rock has been in artists’ toolkits for centuries, which is pretty cool!

And this month, our SciShow Rocks Box subscribers will be getting a beautiful piece of azurite sent right to their doors. Whether you make yours into paints is up to you. If you’d like to sign up for  the Rocks Box subscription, head over to SciShow.

Rocks to learn more. And watch that space, because we’ve got some big announcements coming soon! [ outro ]