Lapis Lazuli: An Article by David Margulies

Copyright - no sections to be used without permission.

Lapis Lazuli - an article by the renowned authority David Margulies

Lapis lazuli was described by Pliny the Elder as 'a fragment of the starry vault of heaven'. It is, and always has been, the most exotic of semi-precious stones and pigments. The best quality blue stone is to be found high in the mountains at Sar-i-Sang, Badakhshan province, north eastern Afghanistan. To our knowledge the oldest use of the lapis lazuli from that source dates back 9,000 years in the form of beads found at Mehrgarh, in present day Pakistan. Lesser quality stone can be found in the same mountain range in today's Tajikistan. Another source for the stone is in the region of Lake Baikal, Siberia. There are deposits in Chile, Canada, America, Angola and Italy.

The Etymology of Azure

Much of the writings about the stone and the pigment are surrounded with myth and mistakes, much by transmitted error. The first myth is that the word lazuli is derived from the Persian, 'lajward'. In fact we do not know where the word originated from. The Old Persian word is 'kasakaina', while Middle Persian was 'Kasken'. The word did find itself transmitted into New Persian. A similar word, 'lazaward', was transmitted into Arabic and thence into Medieval Latin as 'lazzulum' or 'azzurum'. The word was translated into French as 'azur', and into English as 'azure'. The pigment that is obtained from the stone is known in English as 'genuine ultramarine'.

The term 'genuine' is to assist in differentiating it with the synthetically made French ultramarine. French ultramarine was so called because it was a Frenchman, Jean-Baptiste Guimet who won a prize in 1828, offered by the Societe d'Encouragement for developing a synthetic alternative to the mined ultramarine. Ironically, it was the French who named the Holy States, 'Outremer', (in parts of present-day Syria, Iraq and Lebanon) during the First Crusades of 1096 to 1099. The Latin for outremer was 'ultra marinus', 'beyond the sea'. The name of the pigment thus became 'ultramarine' in English.

Early Uses of the Pigment

The earliest known use of the stone is as beads found in Mehrgarh, in present day Pakistan, dating back to 7,000 B.C. The first known use of the pigment was on an Egyptian funerary artefact, circa 1580 to 1550 B.C. The first major use of the pigment was in the Buddhist wall paintings of the Kizil and Dunhuang caves in present-day China from around the 4th to the 6th centuries A.D. During the 15th and 16th Century, one can find the very highest quality ultramarine being used by artists from Northern Europe, extending to Asia. One of the finest examples of the use of ultramarine is in a painting of the Italian Renaissance, 'Bacchus and Ariadne' by Titian, 1521 to 1523, National Gallery, London.

The Mineralogy of Lapis Lazuli

Lapis lazuli is not one mineral but the name given to a collection of up to nine different minerals, some sharing the same elements. The main minerals are lazurite, hauynite, sodalite, noselite, calcite and pyrite. The specific mineral that bears the blue of the pigment is named lazurite. Lazurite comes in two forms, though both are crystals. One form is rock-like, while the other has an isometric crystal structure with the appearance of blue nuggets sitting on a matrix of white calcite crystals. It is the latter that geologists name as lazurite.

It is the quantity of sulphur radical anions trapped within the cubic holes in the lazurite lattice which determines the blue colouring. Even the chemical formulae for lazurite vary depending on location or even from seam to seam.

Genuine vs. French Ultramarine

The main differences between synthetically produced French ultramarine and genuine ultramarine obtained from lapis lazuli are as follows:

1. The pigment particles of French ultramarine are very fine and uniform.
2. The crystals of French ultramarine are of a consistent blue colour.
3. Because French ultramarine crystals are smaller and more regular they diffuse light more evenly.
4. French ultramarine pigment has a strong electro-magnetic reaction, particularly visible if mixed into linseed oil.
5. Genuine ultramarine particles are irregular in size and the shape tends to be conchoidal, that is to say, shell-like.
6. The particles or fractures are more transparent in comparison with French ultramarine. This would explain the luminous quality of the reddish blue paint films of Renaissance, and post-Renaissance paintings.
7. Finally, the major characteristic of the crystal fractures of genuine ultramarine is that they are not uniformly blue. Examined under a microscope, the fractures can vary between those that possess a rich blue colouring, full of sulphur, and others that may appear to be less and less blue; while some will appear to have no blue colouring.

Preparing Pigment from the Stone

There are three ways of preparing pigment from the solid mass:

1. Crushing, grinding, washing and levigating.
2. The 'pastille' method, as exemplified by the recipe of Cennino Cennini, Italian, 15th Century.
3. The froth floatation method; the most common commercial process in use today.

Many commentators throughout the past few hundred years have repeated the axiom that, however blue (or pure) the mass, it will not be sufficient to rely on grinding and washing in order to achieve the best results. As Joyce Plesters of the Scientific Department of the National Gallery, London, has noted: "unless the lapis lazuli from which the pigment is prepared is of exceptional quality, simply grinding and washing produces only a greyish blue powder."