Scanning electron micrograph of crystals of pure salt, sodium chloride. The sample is of an analytically pure laboratory chemical. Salt shows cubic symmetry; the angles between plain faces of the crystals are always at right angles to each other. The particular shape of each crystal is determined by the circumstances of its formation; here, there are elongated prisms, as well as approximations to cubes ( e.g. to left side of the uppermost large crystal ). The amorphous particle on the edge of the crystal to picture right is a contaminant introduced during preparation of the specimen. Salt used in cooking is not as pure as this sample; it may contain additives to ensure free running and absence of caking. Sea salt by its nature contains other minerals that give the salt its prized flavour. Salt has long been a valued commercial product, giving rise to the word salary. Mag x 130 at 10x8