Teaching With Minerals

The following parenthetical note may be read.

[Oh, yes, children, despite its name the board was not chalk - it really was a sliver of a different rock, a thin slate piece covering a goodly part of a wall. (The board could also consist of other stuff made to look and act like the dark gray slate.) The other piece of technology that made the whole thing work synergistically was another mined rock formed into a stylus of sorts; we called this manipulative "chalk," after the rock from which it mostly arose, whitish in color. Usually. As the softer chalk stylus was pressed onto and moved across the harder slate board by hand, it left a trail of chalk dust particles, noticeable white marks against the dark gray board. The particles stuck to the slate semi-permanently so that the marks held, but then they could be dislodged easily by wiping the slate with a piece of cloth, thus cleaning the board and rendering it ready for more such dusty marks. This system may yet be witnessed in some classrooms and other historical places.]