The ferroelectric and pyroelectric properties of mineral and synthetic colemanite were investigated. It is shown that the synthetic compound, prepared by the controlled dehydration of higher order calcium borates, has a much lower Curie temperature than mineral colemanite. The substitutional impurity concentration of strontium for calcium in natural colemanite is proposed to be primarily responsible for its higher Curie temperature. The occurrence of a double dielectric anomaly in some specimens of mineral colemanite is described and it is shown that the temperature at which the lower anomaly occurs is consistent with the ferroelectric transition observed in the synthetic compound while the upper anomaly is characteristic of the more common calcium‐strontium‐borate pentahydrates.