Emeralds

Properties Emerald Aquamarine Morganite Heliodore Goshenite 

Space group P6/mmc Atoms per formula unit Z = 2 apfu 

Habit Well formed prismatic or tabullar hexagonal crystals, with pinacoidal 1010, 0001,  

Color Dark green Blue Pink Golden yellow Colorless 

Pleochroism Green to Blue to Light red to Greenish yellow none 

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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. 

Chromium is used to harden steel, to manufacture stainless steel, and to form many useful alloys. Much is used in plating to produce a hard, beautiful surface and to prevent corrosion. Chromium gives glass an emerald green color and is widely used as a catalyst. 

Synthetic gemstone materials often have multiple uses. Synthetic mby and colodess sapphire are used for watch bearings, unscratchable watch crystals, and bar-code reader windows. Synthetic quartz oscillators are used for precision time-keeping, citizen s band radio (CB) crystals, and filters. Synthetic mby, emerald, and garnets are used for masers and lasers (qv). 

Fig. 4. Schematic diagram of one of the arrangements for the flux-reaction growth of synthetic emerald (2).

For emerald, a hydrothermal reaction arrangement is used, analogous to that of Figure 4. Here the mineralizer is strongly acid, containing 8A[ NH Cl [12125-02-9] and HCl [7647-01-1] to give pH between 0.2 and 4.5. 

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. 

Colored Impregnations. Colored oil to fill cracks is used on gemstones primarily to improve color, most frequendy on emerald. Colored oil is also used to simulate other stones, most frequendy quartz. Depending on the dye used, the colors may fade, in addition to the problems associated with colodess oiling. 

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). 

The only example of xenon in a fractional oxidation state, +, is the bright emerald green paramagnetic dixenon cation, Xe [12185-20-5]. Mixtures of xenon and fluorine gases react spontaneously with tiquid antimony pentafluoride in the dark to form solutions of XeF+ Sb2 F, in which Xe is formed as an iatermediate product that is subsequently oxidized by fluorine to the XeF+ cation (83). Spectroscopic studies have shown that xenon is oxidized at room temperature by solutions of XeF+ ia SbF solvent to give the XE cation (84). 

Properties. Nickel sulfate hexahydrate [10101 -97-0], NiSo 6H20 is a monoclinic emerald-green crystalline salt that dissolves easily in water and in ethanol. When heated, it loses water and above 800°C decomposes into nickel oxide and SO3. Its density is 2.03 g/cm. ... 

TC-Cyclopentadienyl Nickel Complexes. Nickel bromide dimethoxyethane [29823-39-9] forms bis(cydopentadienyl)nickel [1271 -28-9] upon reaction with sodium cyclopentadienide (63). This complex, known as nickelocene, 7T-(C3H3)2Ni, is an emerald-green crystalline sandwich compound, mp 173°C, density 1.47 g/cm. It is paramagnetic and slowly oxidi2es in air. A number of derivatives of nickelocene are known, eg, methylnickelocene [1292-95-4], which is green and has mp 37°C, and bis( 7t-indenyl)nickel [52409-46-8], which is red, mp 150°C (87,88). 

Ammonium Iron(III) Oxalate. This mixed salt [29696-35-3] (NH 2 E (C2 4)3] 374.04, is produced as an emerald-green crystalline... 

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