Abstract
Drill is a Fortran computer program that, based upon crystal structure data, performs the required calculations to build ball and spoke models of crystals. Ball and spoke representations of minerals provide the best representation of the crystal structure of a mineral and are invaluable in teaching and research. Unfortunately, models of complex silicate minerals may contain 500 or more atoms (balls) and cost several thousand dollars. With the aid of Drill, an orienting ball drill, and a supply of plastic balls, these same models can be made at one-tenth, or less, the commercial price. Drill also generates all the atomic positions, bond lengths, and bond angles in the unit cell of a mineral, if given the cell parameters, the general positions of the atoms, and the space group.
