QUARTZ: UNUSUAL PROPERTIES
EPS2 Students: This will not be covered in examinations
Some unusual properties arise from the absence of a center of symmetry in quartz (and tourmaline):
QUARTZ DOES NOT HAVE A center OF SYMMETRY!
The c crystallographic axis is perpendicular to the long axis of uncut crystals.
If the crystal had a center of symmetry, the two ends of these crystals would ha
ve identical properties. However, this is not present. Consequently:
ation of mechanical stress (e.g., compression) along this axis causes
charges of opposite sign at each end (piezoelectricity);
conversely, applied electrical fields produce mechanical
The piezoelectric property makes quartz valuable
in pressure gauges, electronic frequency control devices,
radios, and other applications.
Because no symmetry planes
are parallel to the c axis, crystals may develop either a
left handed or right handed configuration; in nature, the
characteristics of left and right handedness occur