Vibratory tuning fork having a body of piezoelectric material with a base and a pair of tapered tines which extend from the base and decrease in lateral dimension from the base toward the tips of the tines. A crotch section at the base of the tines has an inner pair of faces which lie in crystallographic planes of the piezoelectric material and an outer pair of faces which lie in additional crystallographic planes of the material and extend between the inner pair of faces and the tines. An isolation slot is formed in the base adjacent to the crotch, with enlarged cut-outs at the ends of the slot to prevent the formation of facets and membranes across the slot.