Precious lapis lazuli found its way from the world's most ancient mines to Mesopotamia, Egypt, and Greece. Historicians have written about those traderoutes extensively. In this article, let's dive deeper and discover the geological history of lapis lazuli, as it crystallized in seams of precious rocks in the midst of plate tectonic upheaval. 

By Kathelijne Bonne, 2019.

The mines along the Kokcha river

The story starts four thousand years before Christ. In raging winds, snow, and freezing cold, men cling to 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 rages. High above, merciless 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. The rough wall becomes more brittle due to the sudden contrast in temperature, and large chunks of rock can be cut loose. 

Chunks of rock fall to the ground. Among the rubble, a blue colour becomes visible. The rocks are further processed until the bright blue lapis lazuli can be extracted from the surrounding matrix. 

In the heart of Asia: the Sar-i-sang mines of Afghanistan

Maybe this was everyday practice, in the Sar-i-sang mines, where lapis lazuli for Tutankhamun's funeral mask was 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, 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 lazuli was transported via the trade roads to various exchange 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.

Luxury in Mesopotamia

The most likely ancient source of this stone, although written evidence from Antiquity is lacking, are the high mountains of the Hindu Kush. Lapis lazuli can now also be found at Lake Baikal and in Pakistan, Iran, Chile, Italy and some other areas. 

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. 

Lapis lazuli across the civilizations of the Tigris, Euphrates and Indus

The fertile land around the Tigris and Euphrates was successfully irrigated and cultivated, but in Mesopotamia 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. 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. Shortugai was situated on the Oxus River and was an important centre where lapis lazuli and other desired goods 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 one closer to the afterlife.

Eye shadow of Cleopatra

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 lazuli from Sar-i-sang.

Lapis lazuli: not a mineral but a rock with golden speckles

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.

Lapis lazuli is not one mineral, but a rock that consists of various minerals. The mineral lazurite is responsible for the blueness. 

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 in grains of sand. 

The golden speckles of lapis lazuli are flakes of the mineral pyrite, the famous 'fool's gold', or iron sulphide. High priests of antiquity associated the speckles with the stars. 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 commercial item. 

Sulphur-rich lazurite causes the intense blue colour

To be really precise, lazurite isn't even one, single mineral, it is the sulphur-rich end-member of the oddly-named mineral hauyne. The abundant sulphur causes the intense bright blue colour of lazurite.

We now know what lapis lazuli is. But how was it formed? 

The true origin of lapis lazuli of Afghanistan: colonies of bacteria at the edge of an ancient sea

To understand the origin of the Afghan lapis lazuli, we must delve deeper into the natural history of this Central Asian country. One ancient limestone deposit, which belongs to the oldest in the world, is the original source of lapis lazuli in Afghanistan. 

The limestone was formed during the Archaean eon, an immensely long period in the early history of our planet, which spans from 4 to 2.5 billion years ago. During this time, life arose but remained single-celled. 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 thrived. They performed photosynthesis, the process by which the energy of the sun is used as an energy source. As a by-product, the bacteria produced lime. Layer upon layer of lime was deposited on the seabed, forming matt-like structures. Eventually the algal mats hardened into limestone. 

How the Archean limestones ended up in the middle of Central Asia

Eras later, in Jurassic times, this marine limestone was uplifted above sea level through the action of plate tectonics. Many smaller continents collided with the great old Eurasian continent and now form part of it, as one big puzzle. This huge mountain range now stretches from the Pyrenees over the Alps, Turkey, the Zagros (Iran), the Himalayas and the Tibetan plateau, all the way to the southeast of Asia. The Afghan limestones were squeezed right in the middle of these mountains.  

But the edges of the small continents, hence the lines along which they are glued, are still visible as large fault lines called sutures. They are weak zones in the Earth's crust. 

These weak zones are eroded by rivers, as water always runs alongs the least resisant rock. Hence, the rivers encise themselves along the suture lines and create deep and long valleys. 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.

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. In skarns, ores, rare minerals and gems can be found, making them economically interesting. But for scientists they are a window to the past. 

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. 

Lapis lazuli is a conflict mineral

Lapis lazuli is truly one of Afghanistan's treasures. This country has been war-torn for so long that few people remember 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 in 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. 

Sources.

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.

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

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

Haywood, J. 2000, Atlas of World History. Metro Books. 

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

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

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

Kathelijne Bonne: As an earth scientist and nature lover I am intrigued by how rocks, soil, ocean, air and life interact with each other on geological and human timescales.

Why I started GondwanaTalks.

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