# Resistivity (ρ) & Conductivity (σ) of Metals, Alloys, Rocks, and Soils

Resistivity, also referred to as specific resistance, is dependent on the nature of the material as well as its volume definition (shape and size). Resistivity is expressed in units that are the product of resistance and length; e.g., Ω·cm. The symbol most commonly used for resistivity is rho (ρ).

Conductivity is the reciprocal of resistivity. Conductivity is expressed in units that are the quotient of conductance (Siemens) and length; e.g., S/cm. The symbol most commonly used for resistivity is sigma (σ).

As an example of calculating a volume's resistance, consider the drawing to the left. Assume 12 AWG copper wire with a resistivity (from the table) of 1.72x10-6 Ω·cm, a cross-sectional area (A) of 0.03309 cm2, and a length of 1 meter. Per the given formula, its resistance is:

,

which agrees well with typical specified Ω/km values published by wire manufacturers. Alpha claims 1.59 Ω/1000' or 5.22 Ω/km.

The table of resistivity values below are pulled from Reference Data for Radio Engineers, 1995, Sams Publishing. Please verify accuracy with a second source. See rocks and soils table at bottom. Interesting note: The nickel-silver compound actually contains no silver at all; its name is derived from a silver appearance.

 Metal & Alloy Materials Form Resistivity(x10-6 Ω·cm) Temperature(°C) TemperatureCoefficient (°C-1) Alumel solid 33.3 0 0.0012 Aluminum liquidsolid 20.32.62 67020 .0039 Antimony liquidsolid 12339.2 80020 0.0036 Arsenic solid 35 0 0.0042 Beryllium solid 4.57 20 Bismuth liquidsolid 128.9115 30020 0.004 Boron solid 1.8x1012 0 Brass (66 Cu, 34 Zn) solid 3.9 20 0.002 Cadmium liquidsolid 347.5 40020 0.0038 Carbon diamondgraphitegraphene 5x10201400 1520 -0.0005 Cerium solid 78 20 Cesium liquidsolid 36.620 3020 Chromax (15 Cr, 35 Ni, balance Fe) solid 100 20 0.00031 Chromel solid 70-110 0 0.00011-0.000054 Chromium solid 2.6 0 Cobalt solid 9.7 20 0.0033 Constantan (55 Cu, 45 Ni) solid 44.2 20 0.0002 Copper (annealed) liquidsolid 21.31.7241 108320 0.0039 Gallium solidliquid 2753 300 Gold liquidsolid 30.82.44 106320 0.0034 Granite solid 1x1013 - 1x1015 Hafnium solid 32.1 20 Indium liquidsolid 299 15720 0.00498 Iridium solid 5.3 20 0.0039 Iron solid 9.71 20 0.0052-0.0062 Kovar A (29, Ni, 17 Co, 0.3 Mn, balance Fe) solid 45-84 20 Lava flow (basic)Lava, fresh liquid 1x1012 - 1x1013 Lead liquidsolid 9821.9 40020 0.004 PbO2 solid 92 Lithium liquidsolid 459.3 23020 0.0030.005 Magnesium solid 4.46 20 0.004 Manganese solid 5 20 MnO2 solid 6000000 20 Magnanin (84 Cu, 12 Mn, 4 Ni) solid 44 20 ±0.0002 Mercury liquidsolid 95.821.3 20-50 0.00089 Molybdenum solid 5.174.77 020 0.0033 Monel metal (67 Ni, 30 Cu, 1.4 Fe) solid 42 20 0.002 Neodymium solid 79 18 Nichrome (65 Ni, 12 Cr, 23 Fe) solid 100 20 0.00017 Nickel solid 6.9 20 0.0047 Nickel-Silver (64 Cu, 18 Zn, 18 Ni) solid 28 20 0.00026 Niobium solid 12.4 20 Osmium solid 9 20 0.0042 Palladium solid 10.8 20 0.0033 Phosphor bronze (4 Sn, 0.5 P, balance Cu) solid 9.4 20 0.003 Platinum solid 10.5 20 0.003 Plutonium solid 150 20 Potassium liquidsolid 137 6220 0.006 Praseodymium solid 68 25 Rhenium solid 19.8 20 Rhodium solid 5.1 20 0.0046 Rubidium solid 12.5 20 Ruthenium solid 10 20 Selenium solid 1.2 20 Silver solid 1.62 20 0.0038 Sodium liquidsolid 9.74.6 10020 Steel (0.4-0.5 C, balance Fe) solid 13-22 20 0.003 Steel, manganese (13 Mn, 1 C, 86 Fe) solid 70 20 0.001 Steel, stainless (0.1 C, 18 Cr, 8 Ni, balance Fe) solid 90 20 Strontium solid 23 20 Sulfur solid 2x1023 20 Tantalum solid 13.1 20 0.003 Thallium solid 18.1 20 0.004 Thorium solid 18 20 0.0021 Tin solid 11.4 20 0.0042 Titanium solid 47.8 25 Tophet A (80 Ni, 20 Cr) solid 108 20 0.00014 Tungsten solid 5.48 20 0.0045 W2O5 solid 450 20 WO3 solid 2x1011 20 Uranium solid 29 0 0.0021 Zinc liquidsolid 35.36 42020 0.0037 Zirconiumn solid 40 20 0.0044

 Rock & Soil Materials Resistivity(x10 Ω·cm) Granite 107 - 109 Lava flow (basic)Lava, fresh 106 - 1073x105 - 106 MarbleMarble, whiteMarble, yellow 4x10810101010 Quartz, vein, massive >106 Schist, mica 107 Shale, bedShale, nonesuch 105104 LimestoneLimestone, Cambrian 104104 - 105 SandstoneSandstone, eastern 1053x103 - 104 Clay, blueClay, fire 2x1042x105 Clayey earth 104 - 4x104 Gravel 105 Sand, drySand, moist 105 - 106106 - 105

Posted July 13, 2018