Tellurides, of gold

Tellurium is occasionally found native, but is more often found as the telluride of gold (calaverite), and combined with other metals. It is recovered commercially from the anode muds that are produced during the electrolytic refining of blister copper. The U.S., Canada, Peru, and Japan are the largest Free World producers of the element. 

Tellurium is even less abundant (2 X 10 % of the earth s crust) than selenium. It occurs mainly in sulfide ores, especially with copper sulfide, and as the tellurides of gold and silver. It, too, is obtained from the anode mud from refining of copper. The element forms brass-colored, shiny, hexagonal crystals having low electrical conductivity. It is added to some metals, particularly lead, to increase electrical resistance and improve resistance to heat, corrosion, mechanical shock, and wear. 

HESSITE. A mineral telluride of silver. AgyTe. with some gold, crystallizing in the monoclinic syslem at normal temperatures isometric system above I49.5F (65.3 C). Crystalline form not ohvious at normal temperatures. Hardness. 2-3 specific gravity. 8.24-8.45 color, gray with metallic luster opaque. Named after G.H. Hess (1802— 1850). 

Krennente is another tellunde of gold and silver with a similar composition to sylvanite. but crystallizing in the orthorhombic system. Calaverite is a gold telluride with only a small silver content,... 

Gold occurs mostly native as pure gold. The alloy electrum, gold and silver, is not uncommon. Important gold compounds in ores are tellurides of the type (Ag,Au)Te2-They weather easily and the metal is set free. When it occurs in nature the heavy gold is concentrated in some parts of the sediment as gold sand. 

Monolayers can be transferred onto many different substrates. Most LB depositions have been perfonned onto hydrophilic substrates, where monolayers are transferred when pulling tire substrate out from tire subphase. Transparent hydrophilic substrates such as glass [18,19] or quartz [20] allow spectra to be recorded in transmission mode. Examples of otlier hydrophilic substrates are aluminium [21, 22, 23 and 24], cliromium [9, 25] or tin [26], all in their oxidized state. The substrate most often used today is silicon wafer. Gold does not establish an oxide layer and is tlierefore used chiefly for reflection studies. Also used are silver [27], gallium arsenide [27, 28] or cadmium telluride wafer [28] following special treatment. 

Gold telluride iodide, AuTczI, was the first example of a gold chalco-genide halide, and was found in 1969 (305). Systematic investigations confirmed the existence of at least six compounds four telluride halides and two selenide halides (see Table IV). No sulfide halides have been reported. 

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