Place mint in a wide-mouth pint glass jar, and set aside. Pour vinegar into a nonaluminum saucepan; bring to a boil. Pour hot vinegar over mint in jar and cover with lid. Let stand at room temperature 2 weeks.
Pour mixture through a wire-mesh strainer lined with 2 layers of cheesecloth into a decorative bottle or jar, discarding mint. Seal bottle with a cork or an airtight lid.
Use in vinaigrettes and in fruit or vegetable salads.