Thermal Conductivities* of Selected Substances
Substance	Thermal Conductivity [Watts / m ·°C]
Styrofoam	³ 0.01 (varies)
Still air	0.023 (at 20°C)
Wood	0.08
Dry soil	0.25
Pure Water**	0.60 (at 20°C)
Snow	0.63
Glass	1.05
Wet soil	2.1
Ice	2.1
Sandstone	2.6
Granite	2.7
Lead	34.6
Iron	80.3
Magnesium	159
Aluminum	237
Gold	315
Copper	398
Silver	427

                           *Also known as "heat conductivity."
                            Note that the substances with the highest thermal conductivities are all metals.
                            Generally those substances with high thermal conductivities also have high electrical conductivities.

                         **Pure water is an excellent insulator.  However small concentrations of impurities in water turn it into a
                            conductor.  Even very small concentrations of impurities (such as those in most culinary water) are sufficient
                            to make water a good conductor.