Malachite Pigment

Malachite Pigment

Malachite, the mineral, is a basic carbonate of copper, usually described as a bright greenish blue or sometimes as a pale green. Our malachite is obtained from mines in Nizhniy Tagil, Ural Mountains, Russia, and Hubei Province, China.

Origin and History

It is a historical pigment found in Egyptian tomb paintings as early as the Fourth Dynasty (sixth century B.C.). It received sparse mention in medieval literature probably because it is more commonly found in egg tempera paintings than European oil easel paintings and is often associated with the mineral azurite.

Source

Malachite is basic copper carbonate found in many parts of the world in the upper oxidized portions of copper ore deposits. Notable occurrences include many classic mineral localities such as Shaba, Congo; Tsumeb, Nambia; Ural Mountains, Russia; Mexico; several sites in Australia; England; and several localities in the southwestern United States, especially Arizona, USA. Malachite is a secondary mineral of copper, which means it is formed when copper minerals are altered by other chemicals. It occurs when carbonated water interacts with copper minerals or when a solution of copper interacts with limestone.

Grades

Available from Natural Pigments in two grades or fineness of grind: fine and medium, which produce corresponding light and dark tones of green when used in aqueous medium. This malachite is a fine grade with an average particle size of 20 µ that exhibits a light green masstone with a slightly yellowish undertone. Medium-grade malachite has a particle size range between 60 and 100 microns.

Permanence and Compatibility

Malachite has often proved to be permanent in oil paintings, although it may acquire a dull, brownish hue owing to the darkening of the oil. It is unaffected by exposure to light. In theory, copper carbonate is blackened by sulfur compounds so that it may be affected by exposure to hydrogen sulfide found in polluted air. It is said to be incompatible with sulfide pigments, such as cadmium yellow, orpiment, realgar ultramarine, and vermilion. Even though theoretically subject to blackening when mixed with sulfide pigments, this has never been reported in practice. In tempera paintings, according to A. H. Church [Chemistry of Paints and Painting, p. 200], it is found to have stood well. Malachite passages on Italian frescoes are often still bright green.

Oil Absorption and Grinding

No data has been published on the oil absorption properties of malachite. To be useful as a bright green, it must be ground relatively coarse because, if too finely ground, it becomes too pale for practical use. Cennino Cennini remarks, “if you were to grind it too much, it would come out a dingy and ashy color.” He recommends grinding it in water: “when you have got it worked up, put it into the dish; put some clear water over the color, and stir the water up well with the color. Then let it stand for the space of one hour, or two or three; and pour off the water; and the green will be more beautiful. And wash it this way two or three times, and it will be still more beautiful.” Being moderately low in refractive index, it may be more useful in an aqueous medium like tempera than in an oil medium. However, beautiful results have been achieved with this pigment in oil.

Toxicity

Malachite is moderately toxic, and care should be taken in handling the dry powder pigment to avoid inhaling the dust.

Pigment: Malachite, Fine Grade