Sodalite lapis lazuli

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. 

Nearly all silicates contain some sodium, and there are several silicates which contain relatively large quantities—e.g. soda felspar or albite the soda-lime felspars —e.g. labradorite sodalite nepheline analcime lapis lazuli etc. 

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. 

Lapis lazuli is a metamorphic rock composed of three minerals, blue lazu-rite, white calcite, and brassy pyrite. This stone was highly prized by some cultures, both ancient and modern, because of its intense blue color. Most good-quality lapis lazuli has been mined in Afghanistan and southern Russia, although small deposits have been found elsewhere in the world. Common imitations of lapis lazuli are glass, lazulite (a phosphate mineral), and sodalite (a tectosilicate mineral similar to lazurite). 

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. 

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 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... 

Lazurite (syn., lapis lazuli, lasurite, ultamarine) [Named fromthePersian/azwLuster greasy. Luminescence fluorescent. Cleav e (110) imperfect. Fracture conchoidaL Streak light blue. 

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... 

The key chromophore in ultramarine blue (lapis lazuli), Na6(Al6Si6024)-2NaS3 with sodalite type structure, has been identified by ESR (Fig. 1.41) and resonance Raman spectroscopy as the paramagnetic species. ESR offers a non-destructive method for identification of ultramarine in PVC at a detection limit of 50 ppm for ultramarine blue and... 

Lapis lazuli, or simply lapis, is a rock composed of a mixture of minerals, usually calcite, pyrite and lazurite (qq.v.), with the latter being the dominant constituent. Occurrence is as a blue rock containing brassy yellow crystals (pyrite) with white streaks due to calcite. It is formed from the metamorphism of limestones by an alkaline igneous intrusion (Deer et al., 1992 Rutley, 1988). Other silicate minerals such as hatiyne, sodalite, diopside, forsterite, muscovite and wollastonite (. v.) may also be present. The term is often used incorrectly to refer to the mineral lazurite, which is only one of its components. Lapis lazuli is most famously known from the deposit in the Kokcha River valley, Afghanistan, where it has been mined for more than 6000 years for use in jewellery, as an ornamental stone and as a pigment, ft is also known from Mt Vesuvius (Italy), Colorado and California (USA), Siberia and Chile. 

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... 

Although sodalite is not considered to have been used as a pigment in its own right, its formation in close association with lazurite means that it may be expected to occur as a minor constituent in some lapis lazuli samples (Plesters, 1993). 

Lazurite Sodalite Brilliant ultramarine French blue French ultramarine Gahn s ultramarine Guimet s blue Lapis lazuli Laundry blue Lime blue New blue Oriental blue Permanent blue Permanent mauve Reckitt s blue Royal blue Sky blue Ultramarine yellow Auden Mayer (1962) Buxbaum (1998) 123-131 Carlyle (2001) 472 73, 522 Colour Index (1971) Cl 77007 Harley (1982) 43 Heaton (1928) Linke Adam (1913) 62 Merimee (1830/trans. Taylor 1839) Plesters (1993) Reckitt (1954) Salter (1869) Standage (1892) Zerr Rubencamp (1906/1908) 177-200... 

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