bicolored combination of purple and yellow
trystine, Bolivianite, amethyst-citrine, citrine-amethyst, golden amethyst
Ametrine's appearance is distinctive and otherwise the key quartz indicators will be present (refractive index, birefringence, optic character and optic figure). A bull's-eye optic figure is determinative for quartz. Might also show Airy's spiral.
Stones might be piezoelectric: able to generate electricity produced by mechanical pressure,Pyroelectricity: development of opposite charges at the ends of the axis due to change in temperature and triboluminescent: luminescence produced by friction.