Borate minerals

The principal borate minerals are Hsted ia Table 2. A much more complete listing is available ia the Hterature (3,4). Crystal stmctures of known borate compounds have been compiled (5). 

Borax (tincal), kernite, colemanite, ulexite, probertite, hydroboracite, inderite, datohte, and szaibelyite (ascharite) are the only borate minerals of... 

Boron is comparatively unabundant in the universe (p. 14) it occurs to the extent of about 9 ppm in crustal rocks and is therefore rather less abundant than lithium (18 ppm) or lead (13 ppm) but is similar to praseodymium (9.1 ppm) and thorium (8.1 ppm). It occurs almost invariably as borate minerals or as borosilicates. Commercially valuable deposits are rare, but where they do occur, as in California or Turkey, they can be vast (see Panel). Isolated deposits are also worked in the former Soviet Union, Tibet and Argentina. 

The structural complexity of borate minerals (p. 205) is surpassed only by that of silicate minerals (p. 347). Even more complex are the structures of the metal borides and the various allotropic modifications of boron itself. These factors, together with the unique structural and bonding problems of the boron hydrides, dictate that boron should be treated in a separate chapter. 

The starting aldehyde could have been present on the primeval Earth the question of the necessary boron derivatives is open, although it seems possible that weathering of the borate minerals referred to above could have set free boron salts, which then stabilized the ribose. 

Felmy, A. R. and J. H. Weare, 1986, The prediction of borate mineral equilibria in natural waters, application to Searles Lake, California. Geochimica et Cosmochimica Acta 50,2771-2783. 

The element was discovered in 1808 independently by Sir Humphrey Davy and also by GayLussac and Thenard. Boron does not occur in nature in free elemental form but is found in many borate ores. The principal borate minerals are as follows ... 

There are two broad categories of borates referred to as hydrated and anhydrous. Hydrated borates contain B-OH groups and may also contain interstitial H2O in their structures. Hence, the fully hydrated forms of the fundamental borate units above are B(OH)3 and [B(OH)4] , as found in aqueous solution. The majority of borate minerals and synthetic borates of commercial interest are hydrated. Compositions of borates can be resolved into the form a b B2O3 c H2O (x = 1 for dications x = 2 for... 

Fig. 3. Schematic structures of the calcium borate minerals (a) frovolite, CaO B2O3 4 H2O, (b) pinnoite, MgO B2O3 3 H2O, and (c) vimsite, CaO B2O3 2 H2O (n = infinity)...

BORAX. This hydrated sodium borate mineral, NaiBtOy 101 1, O, is a product of evaporation from shallow lakes and plays. Borax crystallizes in the monoclinic system, usually in short prismatic crystals. Its color grades from colorless through gray, blue to greenish. Vitreous to resinous luster of translucent to opaque character. Hardness of 2-2.5, and specific gravity of 1.715. 

Borates. Minerals composed of compounds of a metal with the borate radical, BO3. 

Boron is a relatively rare element, accounting for only about 0.001% of the earth s crust by mass. Nevertheless, boron is readily available because it occurs in concentrated deposits of borate minerals such as borax, Na2B4C>7 10 H20. 

The borate minerals in this open-pit borax mine near Boron, California, are believed to have been formed by the evaporation of water from hot springs that were once present. 

RTM produces borax decahydrate, borax pentahydrate, anhydrous borax, boric acid (BA), boric oxide, and other specialty borates such as zinc borates from sodium borate minerals. Etibank, a Turkish national mining enterprise, offers borate minerals (colemanite and ulexite) as well as refined borates. 

See, for example, Breslow R., 1959, On the mechanism of the formose reaction, Tetrahedron Lett. 21 22-26 Butlerow, A., 1861, Bildung einer zuckerartigen Substanz durch Synthese. Annalen 120 295-298 and Ricardo, A., Carrigan, M.A., Olcott, A.N., and Benner, S.A., 2004, Borate minerals stabilize ribose, Science 303 196. 

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