Lapis lazuli: following the trace of a blue stone.

11/04/2020

How precious lapis lazuli found its way from the world's most ancient mines to Mesopotamia, Egypt, and Greece, has already been described extensively. Go further and discover the geology of lapis lazuli, as it crystallized in seams of precious rocks in the midst of plate tectonic turmoil.

From the high mountain peaks to the pharaohs.

Text © Kathelijne Bonne.  

Not long ago I watched a documentary, one of the many that have been made on Tutankhamun. I didn't really follow the storyline but I stared, on autopilot, at the Egyptian scenes. Archaeologists with Indiana Jones hats, students, jeeps, hammers, brushes, sand. The pyramids hazy in the distance. Finally, the golden funeral mask appeared on the screen. Now it turns out that the mask may not have been made specifically for the young pharaoh. Maybe it was meant for a queen. Had you noticed the pierced earlobes yet? But that's another story. 

The idea we have of the young pharaoh remains inextricably linked to his funeral mask. The work of art is so stunning that you can look forever at the golden face reflecting the light. How lovely all that gold. And then, waking up from my state of trance, I wondered, where does the blue come from? What is the material around the eyes made of, and that of the eyebrows and the stripes on the so-called Nemes-headdress, which was only reserved for the pharaohs? I started a google search and stumbled upon lapis lazuli. The trace of this blue substance can be followed all the way back via the historic trade routes to the oldest mines in the world. But how did the lapis get there in the first place? What forces led to the creation of such an electric blue piece of rock?

Tutankhamun's funeral mask.
Tutankhamun's funeral mask.

Merciless peaks

Four thousand years before Christ. In raging winds, snow, and freezing cold, men walk a dangerous path on a barren, steep mountain slope. They have walked for days to reach the valley of the Kokcha, where the mines are located. They climb hundreds of meters to get to an outcrop, 1500 meters above the valley floor. Deep below them, the Kokcha River swirls dangerously. High above, merciless mountain peaks tower at more than six thousand metres above sea level. The men enter a narrow shaft, to a depth of about fifty metres. In the light of their torches, they sample the rocky outcrop around them, which is sometimes white, sometimes black. Limestone veins are clearly visible on the barren surface. Below a bright white area, they light up a pile of firewood. The rock face is heated by the flames. With hammers the men loosen the rock face. The rough wall becomes more brittle due to the sudden contrast in temperature, and large chunks of rock can be cut loose. Blue chunks fall to the ground. The pieces on the ground are further processed until the bright blue lapis lazuli can be extracted from the surrounding matrix. 

Hindu Kush (foto: Ninara on Foter.com / CC BY)
Hindu Kush (foto: Ninara on Foter.com / CC BY)

Silk Road

Maybe this was everyday practice, in the Sar-i-sang mines [i], where lapis lazuli for Tutankhamun's funeral mask were unearthed, more than three thousand years ago. We are in the heart of Asia, in Badakhshan, an inhospitable region now partly in Afghanistan. Here, the long, parallel mountain ranges of the Hindu Kush are intersected by deep valleys. On the map, they appear to be bent into a large curve, like a crumpled table cloth. This region was at the crossroads of the trade routes of antiquity, connecting, through time, the civilizations of Europe, Africa, the Middle East to Central Asia and the Far East. 

Lapis lazuli, carnelian, ruby, amber, cut gemstones, silk, ivory, camels, spices, silver, glassware, incense, amphorae, sculptures, etc. were traded on the Silk Road for centuries. Rough lapis was transported via the trade roads to various trading centres, where it was further processed in specialised workshops en-route or at the destination. The exact routes are not known precisely, they may have varied, as they were probably subject to the political stability of the areas to be crossed.

Antiquity's luxury goods 

The most likely ancient source of this stone, although written evidence from Antiquity is lacking, are the high mountains of the Hindu Kush [ii]. Lapis lazuli can now also be found at Lake Baikal and in Pakistan, Iran, Chile, Italy and some other areas [iii]. Lapis lazuli adorns the world's most important archaeological finds such as the pharaoh's funeral mask dating back to 1314 B.C. Numerous, much older art treasures containing lapis lazuli were unearthed in the royal tombs of Ur (~2600 B.C.) in Mesopotamia, including jewellery, musical instruments, game boards, cylinder seals, plaques, beads, amulets, statues, ceramics, furniture and the famous Standard of Ur. 

The Tigris and the Euphrates

The fertile land around the Tigris and Euphrates was successfully irrigated and cultivated, but there was a lack of metals and minerals that needed to be sought after elsewhere. The Sumerians had accumulated enough wealth, and had spare time, to succumb to luxury whims. They could afford to import the luxury goods from far-away places, which is a testimony of the high cultural development of Mesopotamia. 

Lapis lazuli from the Hindu Kush may have been first transferred to the Indus Valley, a civilization with which Mesopotamia had commercial bonds [iv]. There, the commodities were loaded into boats to be shipped to Mesopotamia. There were probably land trade routes as well, e.g. over the Zagros Mountains (now Iran). Moreover, around 2000 BC, the peoples of Indus civilisation had established a trading colony far north of their country, Shortugai, located close to the lapis mines in Afghanistan [iv]. Shortugai was situated on the Oxus River and was an important centre where lapis lazuli and other valuables were processed and distributed.

Possibly, Shortugai was founded only for the lapis mines. The stone was not only in demand as a jewel or decoration, but was also believed to have mystical powers. For priests it symbolized heaven, lapis lazuli brought you closer to the afterlife.

Cleopatra's eye shadow

Ground lapis lazuli was used as a pigment. Cleopatra used it as eye shadow. The stone reached Europe via the Greeks and Romans. Europe's great painters used the powder as a raw material for the colour ultramarine, literally 'from over the sea', which at one time was more expensive than gold. Vermeer's girl with the pearl earring would not be the same without precious lapis from Sar-i-sang.

Golden speckles and sulfur

But what is lapis lazuli? It is a rock of a deep blue colour, speckled with golden spots. The name is derived from the Perzian lazhward, meaning blue. The colour can vary between midnight blue, indigo blue (nili), blue, azure blue, light blue (assemani) to green blue (sabz), according to the Persian names [i]. Lapis lazuli is not one mineral but a rock that consists of various minerals. Responsible for the blue colour is the mineral lazurite. But what is a mineral anyway? As per the official definition, a mineral is a chemical compound formed by natural, geological processes, whose atoms are arranged in a crystal lattice. A common mineral, for example, is kitchen salt, or quartz, as beach sand grains. The golden speckles of lapis lazuli are flakes of the mineral pyrite, the famous 'fool's gold', or iron sulphide. No wonder that the high priests of antiquity associated these speckles with the stars in the heavens. Coarse white pieces in lapis lazuli are the mineral calcite, the most important component of limestone, and this makes the lapis less valuable, at least as a sales item. To be really precise, lazurite isn't even an alone standing mineral, it is the sulphur-rich end-member of the oddly-named mineral hauyne [v]. The abundant sulphur causes the intense bright blue colour of lazurite [iii].

Haüyne (picture: Parent Gery / CC BY-SA 3.0)
Haüyne (picture: Parent Gery / CC BY-SA 3.0)

Bacteria at the seashore

To understand the origin of the Afghan lapis lazuli, we need to delve deeper into the natural history of this country [vi]. We will see how one limestone deposit, which belongs to the oldest in the world, is the original source of the Afghan lapis lazuli. We must turn back the clock to the Archaean 'eon', a very long period in the early history of our planet, which spans from 4 to 2.5 billion years ago. During this time, life arose, still single-celled then. Animals and plants did not yet exist. 

During the Archaean, part of what is now Afghanistan lay on the edge of a sea. There, in this quiet, sunlit, shallow sea, colonies of bacteria lived and thrived. They performed photosynthesis, the process by which the energy of the sun is harvested to produce chemical energy for the bacteria's vital functions. They produced lime as a by-product. Layer upon layer of lime was deposited by the bacteria on the seabed. The build-up of the layers formed matt-like structures, which eventually became limestone. Now we have limestone in the sea, from which the lapis lazuli will later crystallize. But didn't we learn that the lapis lazuli was located in the high mountains of Central Asia, very far from the sea?

From the sea to the mountains

How did the limestone end up in the mountains? To understand this, we must temporarily erase the familiar world map from our minds, and imagine that the continents used to be in other places. The continents are in constant motion, due to the process of plate tectonics. Some of you will have noticed that the forms of Africa and South America fit together. Millions of years ago, both continents were indeed lying side by side. When two continents collide, a mountain range forms. That is what happened with Afghanistan. Since Jurassic times, many smaller continents that are now part of Asia, collided with the great old continent of Eurasia. This is how the large mountain range formed, stretching from the Pyrenees over the Alps, the Turkish high plateaus, and the Zagros (Iran), over the Himalayas and the Tibetan plateau, to the southeast of Asia. Afghanistan lays in the middle of this mountain range.

The Earth's jigsaw puzzle

As a consequence of these different collisions, the smaller continents get crushed between the larger continental blocks of Asia. It is, in essence, a puzzle of several smaller pieces, each with its own history. The small continents are now separated from each other by large fault lines, called sutures. Because these are weak zones in the earth's crust, rivers, as they erode the mountainous terrain, incise themselves along the trace of the sutures. It is, therefore, no coincidence that large river valleys delineate the continental blocks, which can be seen very clearly in Afghanistan. Sar-e-Sang also lies near such a large, intracontinental fault line [vi]. 

Magma kitchen

We now do have limestone, which has come a long way from the sea to the high mountains. We continue to follow the trace, further through time, to lazurite. To put it metaphorically, the formation of lazurite is dependent on a given recipe, that must be produced in a kitchen under special conditions. The ingredients of the recipe are the types of rock needed, in this case a carbonate rock such as limestone. The limestone also requires heating (the kitchen), and certain spices (liquids with reactive elements). Hot, molten rock, i.e. magma, the heat source, comes into contact with the colder limestone. Many chemical reactions occur at the contact between both. 

Magma forms when rock melts deep below the earth's surface and rises to higher regions of the earth's crust. Hot, saturated fluids from the magma, known as hydrothermal fluids, are injected through cracks and fractures of the limestone. These fluids, and the sudden heating they produce, cause the limestone to transform. The minerals in the limestone dissolve to crystallize again as other, new minerals. This process is known in geology as metamorphism. Eventually, lazurite formed in Afghanistan, together with pyrite, diopside, sodalite, forsterite, phlogopite, grenade, dolomite, apatite and afghanite. All these new minerals together form skarn, a type of metamorphic rock [vii]. In skarns, ores, rare minerals and gems can be found, making them economically interesting. But for scientists they are a window to the past. 

Lapis lazuli (blue: lazurite; yellow: pyrite; white: calcite) - picture: Parent Gery / CC BY-SA 3.0
Lapis lazuli (blue: lazurite; yellow: pyrite; white: calcite) - picture: Parent Gery / CC BY-SA 3.0

Half of the planet's history 

This is how Afghan lapis lazuli came into being. Its formation spanned almost half of the planet's history. Archaean limestone deposited by bacteria in the sea, was transported to the high mountains through the 'mill' of plate tectonics. Then the limestone was injected by rising magma, transforming it into an ore-rich skarn deposit. Lazurite was but one of many minerals, but in some placed it was concentrated in large veins. There, high in the Hindu Kush, the lapis lazuli lay for millions of years, until humans stumbled upon it, maybe as early as nine thousand years ago. 

Conflict mineral

Lapis lazuli is truly one of Afghanistan's treasures. This country has been war-torn for so long that few people consider its rich natural and cultural heritage. But it is more critical than ever. Because the bluestone from the oldest mines in the world continues to cause misery. Lapis lazuli is a conflict mineral in any sense of the word. 

Read more on Afghanistan, war, and mineral wealth, as described by Global Witness. 

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Writer's note: 

Do you want to see lapis lazuli? Go to a museum. In most museums on natural history, in the department of mineralogy, you can find lazurite, lapis lazuli and related minerals such as haüyne, sodalite and afghanite. Treasures of Antiquity are obviously in the associated museums, e.g. the Egypt collection in the British Museum and the Grand Egyptian Museum in Cairo. 

Think and ask questions before you buy lapis lazuli and other gemstones, ask about the origin and keep any conflict at the back of your mind.


References.

[i] Wood, John, 1941, A personal narrative of a journey to the source of the river Oxus: by the route of the Indus, Kabul, and Badakhshan, performed under the sanction of the Supreme Government of India, in the years 1836, 1837, and 1838. London: John Murray.

[ii] Moorey, P. R. S. 1999, Ancient Mesopotamian Materials and Industries: The Archaeological Evidence. Eisenbrauns. 

[iii] Schumann, W. 2006, Gemstones of the world. Sterling Publishing Co. Inc. New York. 

[iv] Haywood, J. 2000, Atlas of World History. Metro Books. 

[v] Mindat website. Haüyne. https://www.mindat.org/min-1833.html.

[vi] Siehl, A. 2017, Structural setting and evolution of the Afghan orogenic segment - a review. Geological Society, London, Special Publications, 427, 57-88.

[vii] Earth Science Australia, Skarn Deposits. https://earthsci.org/mineral/mindep/skarn/skarn.html.


Below: a piece of rock from the Sar-i-sang mines, Afghanistan. Lazurite (blue), pyrite (goldish), calcite (white), muscovite (silvery). (picture: Parent Gery / CC BY-SA 3.0).








Lazuriet, pyriet, calciet, muscoviet. (Parent Gery / CC BY-SA 30)