  We present a method for measurements of electric dipole moments on (sub)-mm
size (basalt) particles levitated in an acoustic trap and centered within a
plate capacitor. If an electric field is applied the particles oscillate with
specific frequencies due to their permanent dipole moments. We observe dipole
moments on the order of $D_P = 10^{-15} ... 10^{-14} \rm \, C \, m $. The
dipole moment increases in small aggregates with the number of grains and is
larger for samples vibrated (tribocharged) before trapping. The basalt grains
show no sign of change in their dipole moment during measurements, implying a
timescale for charge mobility being at least larger than minutes.
