The following tables contain the expansion of a selected list of naturally occurring substances, together with a few artificial ones like steel and silica glass for comparison. All the minerals for which high-temperature data are available are included, although some are of more interest as refractories than in geology. A number of other minerals whose expansions have been measured only to 100°C. or less are also included; a much more complete list of these latter will, however, be found in the International Critical Tables. In view of the many irregularities which have been found, extrapolation from these low temperatures to those of greater geologic interest is unsafe.

The tables list the total expansion from 20°C., in per cent of the length or volume at 20°C. The nomenclature in regard to axes, angles, etc., follows Dana’s Textbook of mineralogy (John Wiley and Sons, New York, 1922). For isometric substances only the linear expansion is given; the volumetric expansion may be computed to a close approximation by multiplying the linear expansion by three. For the other crystallographic classes, both linear and volumetric values are quoted. With tetragonal and hexagonal minerals, a change of temperature distorts an original sphere into an ellipsoid of revolution so that . . .