Karen Rosen, age 13, of Great Falls, Mt., for her question:

WHERE DO WE FIND SLATE?

Slate is a dense, fine grained rock formed by shale or clay or more rarely of igneous rocks. Slate is obtained from quarries. In the United States, the most important slate quarries are in Pennsylvania, Vermont, New York, Maine and Maryland.

In Europe slate is quarried in Wales, France and Germany.

Slate is usually quarried in open pits and rarely in underground workings. The stone splits best when it is "green" or freshly taken from the quarry. Slate characteristically splits into thin, broad sheets.

Many rocks that show "slaty cleavage" are by extension loosely called slate. True slate is hard and compact and does not undergo appreciable weathering. The basic minerals comprising slate are quartz and muscovite, a kind of mica; biotite, chlorite and hematite are often present as accessory minerals.

Slate is commonly bluish black or gray black in color. It is used as a roofing material and for paving stones, flooring, blackboards and writing slates.