Datolite

Datolite is an important source of boron in some areas. Boron is used in making items such as flares, rocket fuel igniters, fiberglass, and insulation. In the household, boron is sometimes used in eye drops, powdered soap, bleach, and as a food preservative. Datolite is also processed into gemstones or ornamental stones.

The type localities are in the diabases of the Connecticut River valley and Arendal, Aust-Agder, Norway. Associated minerals include prehnite, danburite, babingtonite, epidote, native copper, calcite, quartz and zeolites. It is common in the copper deposits of the Lake Superior region of Michigan. It occurs as a secondary mineral in mafic igneous rocks often filling vesicles along with zeolites in basalt. Unlike most localities throughout the world, the occurrence of datolite in the Lake Superior region is usually fine grained in texture and possesses colored banding. Much of the coloration is due to the inclusion of copper or associated minerals in progressive stages of hydrothermal precipitation.

It was first observed by Jens Esmark in 1806, and named by him from δατεῖσθαι, "to divide," and λίθος, "stone," in allusion to the granular structure of the massive mineral.