The olive fruit is, at the most, 1 1/2 inches (4 cm) long and 1 1/8 inches (3 cm) in diameter. It varies from roughly apple-shaped to egg-shaped. When mature, but unripe, the olive is green in color; when ripe, it ranges from yellow through red to purplish black. The fruit is of the type botanists call a drupe; it has a hard pit surrounded by flesh. The mature, ripe flesh is 15 to 30 per cent oil by weight.

Since the fruit is easily bruised, it is picked and handled carefully. Food olives are picked by hand, oil olives with mechanical harvesters. Food olives are picked as they begin to ripen and oil olives are picked after they have ripened.

Although most of the United States olive crop is used for food, most of the world's crop is used for olive oil. In the United States, undersized olives and those not suitable for use as food are made into oil.

The oil is obtained by crushing the fruit in hand- or machine-operated presses. It is separated from the watery parts of the juice by skimming or by centrifugation Then it is clarified by washing and settling or by filtration.

The first pressing produces virgin oil, a superior grade that is used for salads, cooking, and medicines, and in canning sardines. It is pale yellow in color, odorless, and easily digested, and it keeps well. Edible oil of inferior quality and slightly greener color comes from a second pressing. Further pressings and, finally, chemical extractions remove most of the remaining oil. Oils from these later extractions are used in lubricants, soaps, and ointments.

Olive oil is from 75 to 80 per cent oleic acid and from 8 to 9 per cent linoleic acid, both unsaturated fatty acids. Spain, Italy, Greece, Turkey, and Tunisia are the major producers of olive oil.

Fresh olives have an unpleasantly bitter flavor. Olives that are to be eaten are pickled (soaked in brine and lye) to rid them of the bitter flavor. (Green olives are not soaked in lye as long as ripe olives and hence are more bitter tasting.) Ripe olives are made uniformly dark by being exposed to air during the pickling process. The entire process can take several months.

The seeds of pickled olives may be removed by hand or machine to make pitted olives. Pitted olives that are hand stuffed with small pieces of pimiento, onion, melon, almond meat, or anchovy are called stuffed olives. All olives are preserved by being heated at a temperature of 240 F. (116 C.) after they are put into cans or bottles.

Fragments and undersized pickled olives are used in relishes, luncheon meats, and salad dressings, and as seasonings.

In the United States most of the olives produced are ripe olives. Most of the green olives eaten in the United States are imported from the Mediterranean countries.

In California the most important varieties of olive are: the Mission olive, widely raised for both food and oil; the Manzanillo, an early ripening variety; the Sevillano, or Queen, largest Spanish olive; and the Ascolano, a large Italian olive.

The common olive is Olea europaea of the olive family, Oleaceae.