Corsi Collection of Decorative Stones

Class XII
Lapis lazuli (Lapis lazzulo)

703. (168) 'There is a stone,' says Pliny 98 'called Cyanus, of dark blue colour, which is sometimes combined with a gold-dust'. Anyone who knows this highly acclaimed and beautiful stone will be convinced that Pliny's description is exact, and will not be able to doubt that the 'Cyanus' of the ancients corresponds to lapis lazuli. Hill 99 concurs with this opinion. That of the ancients came from Persia, and China, now it is also found in Siberia, but it is not as heavy and is inferior in the beauty of its colour; indeed it is often very much marked by white. The presence of iron in lapis lazuli is incidental, and Mineralogists demonstrate by analysis that the ultramarine that is extracted from it is not coloured by any metallic substance. The large altar [p169] of S. Ignazio in the church of the Gesù is ornamented with this stone. The specimen in this collection is entirely azure. (Very rare).

'The Gem which the Ancients called Cyanus is what we now know by the name of Lapis Lazuli, a Stone common among us in the Tops of Snuff-boxes and other Toys; and of which the glorious blue Colour called Ultramarine by the Painters is made,' wrote Theophrastus i .

It was widely believed in Corsi's time that lapis lazuli, a stunningly beautiful blue decorative rock, came mainly from Persia. In fact it has been mined since prehistoric times in the Kotcha valley, in a mountainous region of Badakhshan, Afghanistan ii . Trade routes passed through the valley, carrying the stone to Egypt, Persia (Iran), and other countries in the Middle East and Central Asia, and also to Pakistan, India and China; from all these places it would have been traded on.

The blue mineral is lazurite iii , and it is crushed to make the pigment ultramarine. Corsi is correct in attributing the colour to a non-metallic source; this has been identified as sulphur, an essential chemical constituent. The gold 'stars' in the lazurite 'sky' are crystals of pyrite (iron sulphide), and the white 'clouds', composed of calcite, indicate the nature of the rock, an impure limestone that has been metamorphosed by contact with an intrusion of igneous rock.

Lapis lazuli has also been found south of Lake Baikal in Russia, and more recently in Chile and the USA. It should not be confused with sodalite, a closely related mineral which forms rather more violet blue rocks of which fine examples have come from Canada, Namibia, Bolivia and Brazil. It is more common and less highly valued than lapis lazuli.

i. Theophrastus, tr. Hill (1746) 83-84, note c
ii. Bowersox & Chamberlin (1995) 37-63
iii. Price (2007) 262-263