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MatWeb, The Online Materials Database
Gold, Au
Subcategory: Gold Alloy; Metal; Nonferrous Metal; Precious Metal; Pure Element
Component | Wt. % | | | Au | 100 | |
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Material Notes: Gold is a noble metal and does not react with oxygen. This is why gold does not tarnish. Although it does not form oxides, it will form compounds with other metals and is rarely found in its pure form. It is usually associated with silver and often with mercury. When the silver content is a high, the metal is called electrum, a naturally occurring gold-silver alloy. Gold is also found in tellurides and ore containing quartz where it is either openly visible or enclosed in particles of sulfide minerals such as chalcopyrite, pyrrhotite, pyrite, and arsenopyrite. Gold in its pure form is a very soft metal, so it is often alloyed with other metals for increased strength and hardness. When gold is alloyed, its ductility is diminished, but its malleability remains constant, except when large amounts of copper are added. Red or pink gold (also called rose gold) is gold that contains large percentages of copper and a small amount of silver. Green gold is usually gold alloyed with additional silver or with silver that has a small percentage of copper. White gold is usually 75% gold and 25% nickel (or nickel, zinc, and sometimes copper). Formally white gold was made with silver and/or palladium, but white gold made with nickel and zinc is harder, cheaper, and has better melting characteristics.
Physical Properties | Metric | English | Comments |
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Density | 19.32 g/cc | 0.698 lb/in³ | |
Mechanical Properties |
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Hardness, Vickers | 25 | 25 | |
Tensile Strength, Ultimate | 120 MPa | 17400 psi | Annealed |
Elongation at Break | 30 % | 30 % | |
Modulus of Elasticity | 77.2 GPa | 11200 ksi | 60% Cold Worked |
Poisson's Ratio | 0.42 | 0.42 | |
Shear Modulus | 27.2 GPa | 3950 ksi | 60% Cold Worked; Calculated Value |
Electrical Properties |
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Electrical Resistivity | 2.2e-006 ohm-cm | 2.2e-006 ohm-cm | |
Magnetic Susceptibility | -1.42e-007 | -1.42e-007 | cgs/g |
Thermal Properties |
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Heat of Fusion | 66.2 J/g | 28.5 BTU/lb | |
CTE, linear 20°C | 14.4 µm/m-°C | 8 µin/in-°F | over the range 20-100ºC |
CTE, linear 250°C | 14.6 µm/m-°C | 8.11 µin/in-°F | |
CTE, linear 500°C | 15.2 µm/m-°C | 8.44 µin/in-°F | |
CTE, linear 1000°C | 16.7 µm/m-°C | 9.28 µin/in-°F | at 950°C |
Specific Heat Capacity | 0.1323 J/g-°C | 0.0316 BTU/lb-°F | |
Thermal Conductivity | 301 W/m-K | 2090 BTU-in/hr-ft²-°F | |
Melting Point | 1064.43 °C | 1950 °F | |
Optical Properties |
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Emissivity (0-1) | 0.04 | 0.04 | 1000°C; total spectrum |
Reflection Coefficient, Visible (0-1) | 0.27 | 0.27 | 400 nm |
Reflection Coefficient, Visible (0-1) | 0.5 | 0.5 | 500 nm |
Reflection Coefficient, Visible (0-1) | 0.85 | 0.85 | 600 nm |
Descriptive Properties | |
CAS Number | 7440-57-5 | |
References are available for this material.
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