Lapis Lazuli

The single most useful thing to know about lapis lazuli is that for most of recorded antiquity it was called sapphire.

The Hebrew sappir of the Bible, the Greek sappheiros, and the Latin sapphirus denote lapis lazuli, not the blue corundum that the word means today. The evidence is direct rather than inferential. Pliny the Elder describes sapphirus in the Natural History as a blue stone flecked with gold, which is lapis with its pyrite inclusions, and is not a description of corundum, which has no such flecking. Blue corundum was in any case scarcely known in the Mediterranean before the Roman imperial period. Theophrastus, writing in the fourth century BC in On Stones, describes the same gold-speckled blue material.

The consequences are wide. The sappir of the priestly breastplate in Exodus is lapis lazuli. The pavement of sapphire stone beneath the God of Israel in Exodus 24 is lapis. The throne of sapphire in Ezekiel 1 is lapis. Every medieval and early modern lapidary that discusses the virtues of sapphire before roughly the thirteenth century is discussing, or is drawing on sources that were discussing, this stone.

This is a checkable historical point and not a matter of interpretation, and it is one of the most consistently mishandled facts in popular gem literature, where the biblical passages are routinely illustrated with blue corundum. Where an old text says sapphire, the burden is on the reader to establish which stone is meant, and before the high medieval period the answer is usually lapis.

Lapis lazuli is a rock, not a mineral, an aggregate whose blue comes from lazurite, with white calcite and brass-coloured pyrite as the usual accessories. Lazurite is a sulfur-bearing sodium calcium aluminosilicate, and the colour derives from trisulfide radical anions trapped in the crystal framework, which is an unusual colouring mechanism and the reason the blue is so saturated and so stable.

The economically decisive fact is that for most of history there was essentially one source: the mines of Sar-i Sang in Badakhshan, in what is now northeastern Afghanistan, worked since at least the fourth millennium BC and still worked. Lapis found in the Royal Cemetery at Ur in Mesopotamia, in Egyptian tombs including the funerary mask of Tutankhamun, and in the Indus Valley cities all came from those mountains. The distances are enormous and the trade is one of the best-documented long-range exchange networks of the Bronze Age, traceable precisely because the material is visually distinctive and the source is effectively unique.

Lapis was also the raw material of ultramarine, from ultramarinus, from beyond the sea, the most expensive pigment in European painting. Grinding lapis gives a disappointing grey; the extraction of pure blue required a laborious process of kneading the powder in wax and resin under lye, described by Cennino Cennini in the fifteenth century. The cost was such that ultramarine was specified by contract, priced separately from the painter's fee, and reserved for the Virgin's robe. A synthetic equivalent was produced in 1826 after a prize competition, which collapsed the price and ended the pigment's economic significance.