Malachite
Description
A green mineral composed of Basic copper carbonate. Malachite occurs naturally with the blue copper carbonate mineral called Azurite with malachite being the more abundant of the two. Major deposits of the copper ores have been found in Siberia (Nizhne-Tagilsk), France (Chessy), Nambia (Tsumeb), Congo, Australia (New South Wales), and the U.S. (Bisbee, Arizona). Both malachite and azurite have been used as gemstones and paint pigments since before 3000 BCE. Malachite is prepared as pigment by careful selection, grinding, washing, and levigation. Coarsely ground malachite gives a dark green color while finely ground particles give a lighter more transparent tone. Malachite is a lightfast but is sensitive to acids and sulfur fumes. Basic copper carbonate can also be made artificially by coloring chalk with Copper sulfate. The synthetic pigment, called Green verditer, tends to have regularly sized particles with rounded edges with a paler color than malachite. Natural malachite was occasionally used in tempera based paintings before the 16th century and later, green verditer was used for both distemper and oil based interior house paints in the 19th century. Malachite is also found as a corrosion product on metallic Copper.
Synonyms and Related Terms
basic copper carbonate; Pigment Green 39; CI 77492; Berggrün (Deut.); Malachit (Deut.); verdetto della Magna (It.); malachito (It.) malaquita (Esp.); malaquite (Port.); malachite (Fr., It.); malachitis (Gr.); malachiet (Ned.); rokusho (Jap.); iwarokusho (Jap.); byaku roku (Jap.); shih lü; (Chin.); spang (Tibetan); verde azzurro; basic cupric carbonate; green hydrous copper carbonate; green bice; Bremen green; green verditer; Hungarian green; mountain green; mineral green; copper green; iris green; Olympian green
Physical and Chemical Properties
Insoluble in water and ethanol. Decomposes in acids with the evolution of carbon dioxide bubbles. Decomposes with warm alkalis. Stable in light.
Perfect cleavage in one direction. Streak = green. It is a brittle mineral that fractures conchoidally with splinters. Pigment particles are coarse and irregular.
Under the polarizing light microscope, malachite is coarse (broad particle size distribution). It has perfect cleavage and the crystalline structure is immediately apparent. Shapes can be euhedral with tabular forms, and are sometimes even prismatic. Banding often apparent in some particles. Smaller particles can appear as shards, (acicular) needle-shapes, or columnar-shapes. Larger particles are often observed often to be fibrous agglomerates or botryoidal masses (grape-like clusters) that do not go to complete extinction in XPL. Larger particles are pale green to blue-green with smaller particles almost colorless. Relief is moderate (and variable upon stage rotation). RI > 1.662 in β and gamma directions but RI = 1.655 in alpha direction. Malachite is strongly birefringent with higher order jewel tones observed (although thinner, smaller particles may exhibit high first-order tones). Some anomalous blues can be seen. Extinction is straight (although some have reported inclined).
| Composition | CuCO3-Cu(OH)2 |
|---|---|
| CAS | 12069-69-1 |
| Mohs Hardness | 3.5 - 4.0 |
| Density | 3.9-4.0 |
| Refractive Index | 1.655; 1.909; 1.875 |
Hazards and Safety
Skin contact and inhalation may cause irritation or allergic reactions. Chronic exposure may cause anemia.
Turns black with warm alkalis, hydrogen sulfide or sulfur fumes.
Comparisons
Properties of Common Gemstones
Additional Images
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Malachite PPL 400x
Malachite XPL 400x
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Sources Checked for Data in Record
- Nicholas Eastaugh, Valentine Walsh, Tracey Chaplin, Ruth Siddall, Pigment Compendium, Elsevier Butterworth-Heinemann, Oxford, 2004
- Encyclopedia Britannica, http://www.britannica.com Comment: Retrieved June 5, 2003.
- The Dictionary of Art, Grove's Dictionaries Inc., New York, 1996 Comment: 'Pigments'
- Wikipedia: http://en.wikipedia.org/wiki/Malachite (Accessed Sept. 10, 2005)
- R. J. Gettens, G.L. Stout, Painting Materials, A Short Encyclopaedia, Dover Publications, New York, 1966 Comment: density=4.0, ref index=1.655; 1.909; 1.875
- G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971
- Ralph Mayer, A Dictionary of Art Terms and Techniques, Harper and Row Publishers, New York, 1969 (also 1945 printing)
- C.V.Horie, Materials for Conservation, Butterworth-Heineman, London, 1997
- R.D. Harley, Artists' Pigments c. 1600-1835, Butterworth Scientific, London, 1982
- Jack Odgen, Jewellery of the Ancient World, Rizzoli International Publications Inc., New York City, 1982
- A.Lucas, J.R.Harris, Ancient Egyptian Materials and Industries, Edward Arnold Publishers Ltd., London, 4th edition, 1962
- Thomas B. Brill, Light Its Interaction with Art and Antiquities, Plenum Press, New York City, 1980
- Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976
- The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998
- Art and Architecture Thesaurus Online, http://www.getty.edu/research/tools/vocabulary/aat/, J. Paul Getty Trust, Los Angeles, 2000
- Pigments Through the Ages - http://webexhibits.org/pigments/indiv/overview/malachite.html
- CRC Handbook of Chemistry and Physics, Robert Weast (ed.), CRC Press, Boca Raton, Florida, v. 61, 1980 Comment: density=3.7-4.1