Sodalite ultramarine

Ultramarine, analcite, NaPt Basic sodalite, ultramarine... 

Figure 2.29 The Sodalite/Ultramarine framework, which results by sharing of the square faces of the 024h orbit truncated octahedron over the extended lattice again, shown as a decoration of vertices of the cube. 

Feldspar group Silicates group Lazurite Sodalite Ultramarine Derrick eta/. (1999) 134-138... 

Azurite Calcite Diopside Forsterite Hauyne Lazurite Muscovite Pyrite Sodalite Ultramarine Wollastonite... 

Azurite Calcite Diopside Forsterite Hauyne Indigo Muscovite Pyrite Quartz Sodalite Ultramarine Azure Bleu degarance Lapis lazuli Aston et al. (2000) 39—40 Cennini (c. 1400/Thompson, 1960) 37-38 Clarke (2001) 2790 Deer et al. (1992) 500 Desormes Clement... 

Zeolites are structurally related to colorless sodalite, Na4Cl[Al3Si3012], and to deeply colored ultramarines. These have aluminosilicate frameworks that enclose cations but no water molecules (Fig. 16.25). Their special feature is the additional presence of anions in the hollows, e.g. Cl-, S()4, S2, or S. The two last-mentioned species are colored radical ions (green and blue, respectively) that are responsible for the brilliant colors. The best-known representative is the blue mineral lapis lazuli, Na4S (.[Al3Si3012], which is also produced industrially and serves as color pigment. 

Obviously, in solution, 83 is not stable against oxidation. It is stable in the mineral lapis lazuli, and the industrial ultramarine blue pigment [28]. In these materials, the radical 83 is encapsulated in the -cages of the sodalite structure, which protects it against oxidation. In ultramarine pigments, another radical anion polysulfide, 82 , has been observed. 

Research in zeolites has also branched out to try to prepare new materials by incorporating various molecules and ions in the cages of these microporous and mesoporous structures. An early example of this was the preparation of the pigment ultramarine used in many paints and colourants. It is based on the zeolite sodalite (SOD) structure and contains 83 ions trapped in the cages this is the same anion found in the mineral lapis lazuli, to which it imparts the beautiful deep blue colour. Treatment of zeolites such as Na-zeolite Y with sodium vapour traps Na4 ions in the cavities, which impart a deep red colour. 

The structure of sodalite, Na lsSiaO Gl, a representative crystal of the framework class, is shown in Figure 13-13. It is interesting that the same framework is present in ultramarine (lapis lazuli).07 In the ultramarines sulfur complexes, Sx—, to which the blue color is attributed, are present in place of chlorine. The selenium and tellurium analogues are blood-red and yellow, respectively. 

Ultramarine is essentially a three-dimensional aluminosilicate lattice with entrapped sodium ions and ionic sulfur groups (Fig. 32). The lattice has the sodalite structure, with a cubic unit cell dimension of ca. 0.9 nm. In synthetic ultramarine derived from china clay by calcination (see Section 3.5.3), the lattice distribution of silicon and aluminum ions is disordered. This contrasts with the ordered array in natural ultramarines. 

A semiprecious deep-blue gem lapis lazuli has been known from ancient times and is available in synthetic forms under the name ultramarine. These are aluminosilicates of the sodalite type that contain sulfur in the form of the radical anions S3 and S2. The former, always present, causes a deep-blue color, and when S2 is also present a green hue is produced. 

The ultramarine and sodalite framework lattice is shown in Figure 2.29. This framework results when the square faces of the truncated octahedron are shared. Again, the perspective in the figure emphasizes the possibility of constructing the extended lattice of P4-3m symmetry. 

Another class of framework aluminosilicates is the ultramarines. They are characterized by an open framework and intense colors. They diller from the previous examples by having free anions and no water in the cavities. Ultramarine blue, which is the synthetic equivalent of the mineral lapis lazuli, contains radical anions. SjT and ST. The dominant Sj gives rise to its blue color. Ultramarine green also contains the.se two anions but in comparable amounts. Although these two anions are also found in ultramarine violet and pink, the characteristic color is due to a third species, perhaps or S - - Structurally related, but colorless, minerals such as sodalite (containing chloride unions) and noselite (containing sulfate anions) are sometimes included in the broad category of ultramarines. 

Ultramarines. The last group of framework silicates that we shall mention includes the materials called ultramarines, the coloured silicates which have been manufactured for use as pigments. The mineral lapis lazuli is of the same type, and since a number of colourless minerals such as sodalite are closely similar in structure, we shall for simplicity refer to all these silicates as ultramarines. Like the other framework silicates they are based on (Si,Al)02 frameworks with positive ions in the interstices, but a characteristic of the crystals of this group is that they also contain negative ions such as Cl", SOj , or S . Like the felspars and in contrast to the zeolites the ultramarines are anhydrous. Formulae of representative members of the group are ... 

The synthesis of zeolites can be traced back to the nineteenth century, when Jean-Baptiste Guimet was able to produce an artificial version of the highly valued and expensive natural pigment ultramarine, an aluminosilicate sodalite containing polysulfides in its cavities. For this discovery he was awarded a French national prize in 1828. In 1862 another French chemist, St Claire Deville, synthesised an analogue of levyne... 

The beautiful blue and turquoise colours observed in natural forms of sodalite (examples of which are known as lapis lazuli and ultramarine) are known to result from the inclusion of sulfide 83 (blue) and smaller concentrations of 82 (yellow) chromophores within the sodalite cages. 8imilar materials based... 

Ultramarines are bright blue pigments based on a zeolite (sodalite) that hosts the colour centres [Sa] and [S3]. Ultramarines include lapis lazuli and have been in use for over 5500 years. The UV-VIS spectrum of [SJ exhibits a broad band centred at 370nm, while [83] absorbs at 595 nm. (a) Draw Lewis structures for [82] and [83] . What shape is the [83] ion (b) Why can EPR spectroscopy be used to study these ions Suggest a reason why both... 

Schlaich H, Lindner G, Feldman J et al (2000) Optical properties of Se2 and Se2 color centers in red selenium ultramarine with the sodalite structure. Inorg Chem 39 2740-2746 Schott S, Rager H, Schurmann K, Taran M (2003) Spectroscopic study of natural gem quality Imperial - topazes from Ouro Preto, Brasil. Eur J Miner 15 701-706 Scott M, Henderon B, Gallagher H, Han T (1997) Optical spectroscopy of (MnOa) and (V04) in Srio(V04)F2. J Phys Condens Matter 9 9893-9897 Shionoya S, Yen W (1999) Phosphor handbook. CRC Press, Boca Raton... 

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