What Property Makes Quartz Valuable as an Abrasive?

Silicon Dioxide

• Quartz is made of silicon dioxide, the same substance that comprises glass and sand. In silicon dioxide, atoms of silicon and oxygen are connected in a continuous, three-dimensional network; this is in contrast to substances such as water in which each molecule is a clearly-defined unit made up of a small group of atoms. For water, each molecule exists as an independent unit, and molecules cling together by relatively weak forces. The network structure of silicon dioxide is held together with strong bonds, making it a hard substance.

Hardness and the Mohs Scale

• Hardness is the property of materials to resist scratching or deforming; one way of determining hardness is to see if one substance can scratch another. Quartz measures seven on the Mohs scale used by scientists to rate the hardness of materials. At the bottom of the scale is talc with a rating of one; diamond is the hardest with a rating of 10. The Mohs scale is relative and only gives an indication of what materials scratch others; those with higher ratings can scratch any materials rated lower.

Sharp-Edged Crystals

• Another feature of quartz that makes it a good abrasive is its crystal structure; when quartz breaks, it cleaves along the crystal faces, leaving sharp edges that assist in grinding. During abrasive operations, quartz may fragment when brought into contact with other hard materials, but the fragments also have sharp edges.

Quartz and Sand

• Sand grains, composed largely of quartz, are widely employed as abrasives. Because quartz̵7;s crystal structure extends down to the atomic level, grains of almost any size retain abrasiveness while being useful for different tasks. Larger grains, for example, are better at grinding away substantial amounts of material, whereas smaller grit sizes are suited for smoothing and polishing.