On the other hand, we can affirm with the greatest certainty, that the sapphire of the ancients was our lapis lazuli. The latter is of a blue colour, which inclines sometimes to violet or purple, and which is often very dark. It is altogether opake, yet its colour will admit of being compared to a sky-colour; in mentioning of which Pliny had no idea of transparency, for he compares the colour of an opake jasper to a sky-blue[1446]. The lapis lazuli is interspersed with small points, which were formerly considered as gold, but which are only particles of pyrites or marcasite. It can be easily cut and formed into articles of various kinds, and at present it is often used for seals. Pliny, however, informs us that it was not fit for this purpose when it was mixed with hard foreign particles, such as quartz; and that which was of one colour was therefore much more esteemed[1447]. Many cut stones of this kind, which are considered as antiques, may be found in collections. I remember to have seen several works of this sort in the excellent collection of the duke of Brunswick, which, in all probability, are Egyptian, and which are worthy of an accurate description. That lapis lazuli was used formerly for inlaid works I am well convinced, though at present I can produce no proofs. In how beautiful a manner it is employed for that purpose in Florentine works, is well known. The largest and most magnificent squares of lapis lazuli which I ever saw, are in the apartments at Zarskoe-Selo, a summer palace near Petersburg, belonging to the empress of Russia, the walls of which are covered with amber, interspersed with plates of this costly stone. I was informed that these plates were procured from Thibet. The doubt expressed by Epiphanius concerning stairs overlaid with lapis lazuli, respects only the great expense of it, and he perhaps imagined that the steps were entirely cut from the solid stone. The confounding the sapphire with the cyanus, or comparing it to it, of which several instances occur, proves that the former must have had a great resemblance to copper-ore; for that the cyanus is a kind of mineral or mountain blue, tinged with copper, I have proved already[1448]. The blue colour of lapis lazuli has always been supposed to be owing to copper; but according to the latest discoveries it originates from iron[1449]. The medicinal effects which the ancients ascribed to their sapphire could be produced only from a mixture of copper, as they considered the Armenian stone, or false lapis lazuli, to be the real kind. They recommended copper ochre for an inflammation of the eyes[1450]. In the last place it agrees with what Dionysius says, that the sapphire or lapis lazuli was produced in veins among other kinds of stone[1451]. The sapphire also mentioned in the oldest writings of the Hebrews, appears to be no other than the sapphire of the Greeks, or our lapis lazuli; for it was said likewise to be interspersed with gold points[1452].
The ancients therefore were acquainted with our lapis lazuli; but the question whether they used it as a paint, or prepared ultramarine from it, I cannot answer with sufficient certainty. It is possible that their cæruleum sometimes may have been real ultramarine; but properly and in general it was only copper ochre[1453]. The objection that the ancients made blue glass and blue enamel, and if they had not smalt they could use no other pigment that would stand fire but ultramarine, I shall answer in the next article.
Before I proceed to the oldest information with which I am acquainted respecting ultramarine, or the blue colour made from lapis lazuli, I shall communicate what I know of the origin and antiquity of the name commonly given to this stone. That I might be able to offer something more on the subject than what has been said by Salmasius[1454], I requested the opinion of Professor Tychsen, which, with his permission, I have here subjoined[1455]. It is, in the first place, certain that the word is of Persian derivation, and the stone, as I have already remarked, has hitherto been brought to us from Persia. Secondly, it signifies a blue colour. It was at first also the common name in Europe for blue stones and blue colours used in painting; and it was a long time used to express mountain-blue impregnated with copper. The modern systematic mineralogists, it appears, first appropriated the corrupted Persian word to the present lazur-stone, properly so-called; and those therefore would commit an error in mineralogy who should now apply this name to the Armenian stone, mountain-blue, or any other blue mineral containing copper.
Without pretending to have discovered the first mention of the name lazuli in those writings which have been handed down to us, I shall here offer, as the oldest with which I am acquainted, that found in Leontius[1456], who, where he gives directions for colouring a celestial globe, speaks of lazurium. If Fabricius be right, Leontius lived in the sixth century[1457]. Among the receipts for painting, written in the eighth century, which Muratori[1458] has made known, we find an unintelligible account how to make lazuri, for which cyanus compositus, perhaps a prepared kind of mountain-blue, was to be employed. There is also another receipt which orders blue-bottles to be pounded in a mortar. It appears therefore that this word was used in the corrupted Latin of that period to signify a blue colour for painting. The same word, formed after the Greek manner, seems to have been used for blue by Achmet, the astrologer, who lived in the ninth century[1459], and by Nonus in the tenth for a blue earth[1460]. Of still more importance is a passage of Arethas, who lived in the following century, and who, in his exposition of a verse in the book of Revelation[1461], says, the sapphire is that stone, of which lazurium, as we are told, is made[1462]. This, therefore, is a strong corroboration that the sapphire of the ancients was our lapis lazuli, and appears to be the first certain mention of real ultramarine. The word however occurs often in the succeeding centuries for blue copper-ochre. Constantinus Africanus, a physician of the eleventh century, ascribes to lapis lazuli the same medicinal qualities as those of copper-ochre[1463]; as do also Avicenna, Averroes, and Myrepsius. The first, under the letter lam, gives a chapter entitled lazuard, to which the translator has prefixed “De azulo, id est, de lapide Armenio;” and the last says expressly, that the lapis lazuli of the Latins is the lazurios of the Greeks[1464]. The words azura, azurum, azurrum, occur often also in that century for blue.
The name ultramarine, or, as it was first called, azurrum ultramarinum, I have not yet found in any writer of the fifteenth century. But it appears that it must have been common about the end of that century, as it was used by Camillus Leonardus in 1502[1465]. It is probable that it originated in Italy. In the first half of the sixteenth century Vanuccio Biringoccio gave directions for preparing the real ultramarine, which he distinguishes with sufficient accuracy from copper azur[1466], or, as he calls it, the azurro dell’ Alemagna. At that period, however, the best method of preparing it must have been doubtful as well as little known, and on that account of no great benefit; for, in the beginning of the sixteenth century, the father of the celebrated Giambatista Pigna, an apothecary at Modena, was in possession of the secret for making the best ultramarine, by which he acquired more riches than would have arisen from a large estate[1467]. It is not, therefore, altogether true that Alexius Pedemontanus, as Spielmann relates[1468], was the first person who mentioned ultramarine. I am of opinion that this Alexius, or Hieronymus Ruscellai concealed under that name, who wrote in the beginning of the sixteenth century, only first published a complete account of the method of preparing it. At any rate, his receipt was long followed as the best and the most certain[1469]. But on what information is that assertion founded, which we read in English and French authors[1470], that the preparation of ultramarine was found out in England, and that a servant of the East India Company disclosed it, in order to be revenged for some injury which he had sustained?
[The following is the method of making ultramarine from lapis lazuli. The finest mineral is selected, heated to a dull red heat, and quenched in water; it is thus rendered friable, and is ground down into an impalpable powder. This is then mixed with a tenacious paste made of linseed oil, wax, resin, turpentine and mastic; and the mixture being kneaded in warm water gives out the blue particles, which are afterwards collected by subsidence.
Chemists are not agreed concerning the cause of the colour of ultramarine. Dr. Eisner considers it to arise from sulphuret of sodium and of iron, the former being a higher sulphuret than the latter. MM. Clement and Desormes show that the iron is not essential, either to the lapis lazuli, or to the pigment made from it.
An artificial method of making ultramarine was discovered in 1828 by M. Guimet; the process has been kept secret. Processes have also been discovered by M. Gmelin of Tübingen, M. Persoz of Strasburg, and others. M. Gmelin’s process consists in fusing a mixture of two parts of sulphur and one of dry carbonate of soda in a Hessian crucible, and then sprinkling into it by degrees another mixture of silicate of soda and aluminate of soda. The crucible must be exposed to the fire for an hour after this. The ultramarine thus prepared contains a little sulphur, which can be separated by means of water.
Some valuable observations on this subject have lately been published by M. Prückner[1471]. He states that the materials required in the preparation of ultramarine are alumina, sulphate of soda, sulphur, charcoal and a salt of iron, the common sulphate or green vitriol being the best. The alumina is supplied in white bole, or a very pure white clay. The sulphate of soda is reduced by charcoal and heat to the state of sulphuret, and its solution thus obtained afterwards boiled with sulphur so as to form a persulphuret (penta-sulphuret, Berz.). The solution is then mixed with the dried clay and stirred; during the mixing a solution of green vitriol is added and mixed. It is then dried and very finely powdered as rapidly as possible. It is afterwards heated in a muffle; then washed, drained and again heated in a muffle; finally it is again washed, dried and powdered.]