Beryls

Although there is general agreement that the broad band centred at 16,100 cm-1 causing the blue colour of aquamarine represents a Fe2+ — Fe3+ IVCT transition (table 4.2), uncertainty exists over the assignments of two other bands at 12,200 cm-1 and 10,300 cm-1 (Farrell and Newnham, 1967 Wood and Nassau, 1968  

In optical spectra of emerald (Neuhaus, 1960 Poole, 1964 Wood and Nassau, 1968 Schmetzer and Bank, 1981), Cr3+ CF bands are located near 16,130 cm-1 and 23,530 cm-1 and are assigned to cations in octahedral sites. Similar bands for octahedral V3+ ions in beryl occur around at 16,000 cm-1 and 23,800 cm-1 (Beckwith and Troup, 1973 Schmetzer, 1982 Ghent and Lucchesi, 1987). Spectral features of pink and red beryls in the region 18,000-20,000 cm-1 (Wood and Nassau, 1968) may originate from crystal field transitions in Mn3+ ions in morganite. 

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The alkali metals of Group I are found chiefly as the chlorides (in the earth s crust and in sea water), and also as sulphates and carbonates. Lithium occurs as the aluminatesilicate minerals, spodimene and lepidolite. Of the Group II metals (beryllium to barium) beryllium, the rarest, occurs as the aluminatesilicate, beryl-magnesium is found as the carbonate and (with calcium) as the double carbonate dolomite-, calcium, strontium and barium all occur as carbonates, calcium carbonate being very plentiful as limestone. 

Gr. beryllos, beryl also called Glucinium or Glucinum, Gr. glykys, sweet) Discovered as the oxide by Vauquelin in beryl and in emeralds in 1798. The metal was isolated in 1828 by Wohler and by Bussy independently by the action of potassium on beryllium chloride. 

Beryllium is found in some 30 mineral species, the most important of which are bertrandite, beryl, chrysoberyl, and phenacite. Aquamarine and emerald are precious forms of beryl. Beryl and bertrandite are the most important commercial sources of the element and its compounds. Most of the metal is now prepared by reducing beryllium fluoride with magnesium metal. Beryllium metal did not become readily available to industry until 1957. 

Scandium is apparently much more abundant (the 23rd most) in the sun and certain stars than on earth (the 50th most abundant). It is widely distributed on earth, occurring in very minute quantities in over 800 mineral species. The blue color of beryl (aquamarine variety) is said to be due to scandium. It occurs as a principal component in the rare mineral thortveihte, found in Scandinavia and Malagasy. It is also found in the residues remaining after the extrachon of tungsten from Zinnwald wolframite, and in wiikite and bazzite. 

Berthelot) reagent Berthierine [12178-37-9] Bertholet s silver Bertrandite [12161-82-9] Beryl... 

Several gemstone species occur in various colors, depending on the presence of impurities or irradiation-induced color centers. Examples are the beryl, comndum, and quart2 families. Quart2 has poor optical properties (RI = 1.55, DISP = 0.013), but becomes of gemological interest when it exhibits attractive colors. Any material can have its color modified by the addition of various impurities synthetic mby, sapphires, and spinel are produced commercially in over 100 colors (2). Synthetic cubic 2irconia has been made in essentially all colors of the spectmm (11), but only the colorless diamond imitation is produced commercially in any quantity. 

Beryl. Beryl [1302-52-9] Be Al Si O g, is called aquamarine [1327-51 -1] when pale green or blue from inclusion of Fe emerald [12415-33-7] when dark green from Cr or at times V, and morganite or red beryl when pink or red, respectively, from Mn. Only the synthetic emerald is in commercial production, although the other colors can also be grown. Both the flux and hydrothermal techniques are used to grow this luxury synthetic. 

A thin layer of dark green beryl had been grown by a hydrothermal technique over the surface of a pale beryl to imitate emerald. It has been suggested that such stones should be called synthetic emerald-beryl doublets (16). The abiHty to grow thin, but not thick, single-crystal diamond on the surface of natural diamond (17) leads to the possibiHty of growing such a thin film colored blue with boron this has been done experimentally (18). 

Occurrence The beryUium content of the earth s surface rocks has been estimated at 4—6 ppm (1). Although ca 45 beryllium-containing minerals have been identified, only beryl [1302-52-9] and bertrandite [12161 -82-9] are of commercial significance. 

Open-pit mining, and the fact that the beryUium may be extracted by leaching with sulfuric acid. Although some beryl is processed, the majority of beryUium is now obtained from bertrandite. 

The largest consumption of beryUium is in the form of aUoys, principally the copper—beryUium series. The consumption of the pure metal has been quite cycHc in nature depending on specific governmental programs in armaments, nuclear energy, and space. The amount of beryUium extracted from bertrandite has tanged between 200 and 270 metric tons pet year since 1986 (14). SmaU quantities of beryl were also processed during this period. 

The commercial ores, beryl and bertrandite, are usually decomposed by fusion using sodium carbonate. The melt is dissolved in a mixture of sulfuric and hydrofluoric acids and the solution is evaporated to strong fumes to drive off siUcon tetrafluoride, diluted, then analy2ed by atomic absorption or plasma emission spectrometry. If sodium or siUcon are also to be determined, the ore may be fused with a mixture of lithium metaborate and lithium tetraborate, and the melt dissolved in nitric and hydrofluoric acids (17). 

Tetramethylethylenediamine dihydrochloride [7677-21-8] M 198.2, m -300°. Crystd from 98% EtOH/conc HCl. Hygroscopic. [Knorr Chem Beryl 3510 7904.]... 

On silicon carbide, it is easier to see and measure step heights than in crystals like beryl, because SiC has polytypes, first discovered by the German crystallog-rapher Baumhauer (1912). The crystal structure is built up of a succession of close-packed layers of identical structure, but stacked on top of each other in alternative ways (Figure 3.24). The simplest kind of SiC simply repeats steps ABCABC, etc., and the step height corresponds to three layers only. Many other stacking sequences... 

The discovery of beryllium in 1798 followed an unusual train of events. The mineralogist R.-J. Haiiy had observed the remarkable similarity in external crystalline structure, hardness and density of a beryl from Limoges and an emerald from Peru, and suggested to L.-N. Vauquelin that he should analyse them to see if they were chemically identical. As a result, Vauquelin showed... 

Both beryl and emerald were found to be essentially Be3Al2Si O g, the only difference between them being that emerald also contains 2% Cr, the source of its green colour. The combining weight of Be was 4.7 but the similarity (diagonal relation) between Be and... 

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