Verona Green Earth is the natural mineral celadonite, a greenish phyllosilicate mineral of potassium and iron in both oxidation states, aluminum hydroxide, and numerous trace elements. The color of celadonite varies considerably from pale green, bright green, bluish-green, olive-green, and black-green, depending upon its constituent elements. Our Verona green earth is from deposits in northern Italy near the famous sources of Veronese green earth.
|Common Names (mineral):||Simplified Chinese: 绿鳞石 |
German: Celadonit, Celedonit, Grünerde, Seladonit, Veronit
Spanish: celadonita, Veronita
|Common Names (pigment):||English: green earth |
French: terre verte
Italian: terre verde
Spanish: terra verde
|Synonyms (mineral):||Baldogée, Celedonite, kmaite, Seladonite, Verona Earth, Veronite, Yanit|
Origin and History
The word glauconite is derived from the Greek word glaucos, originally meaning gleaming, later bluish green, and then silvery or gray. It has been in painting since ancient times. Restorers have proved through X-ray diffraction that the famous pigments of past centuries known as Veronese and Bohemian terre verte are, in essence, glauconite.Source
Green earth, also widely known as terre verte, is primarily composed of the minerals celadonite and glauconite. The presence of celadonite or glauconite, minerals of complex silicate composition, produces colors that vary from cold bluish greens to warmer yellow and olive hues. It may have been formed originally from biotite (a dark-colored mica), but other minerals, and even organic matter, may change it into glauconite. The mineral has a micaceous structure, a silicate crystallized in monoclinic forms that readily separates into very thin leaves. It is characteristically formed on submarine elevations of ancient seabeds ranging in depth from 30 to 1,000 meters (100 to 3,300 feet) below sea level and in the sedimentary rocks of different geological systems. Usually, it forms small (from 0.8 to 1.5 mm in diameter) green round or angular grains.
Type locality, also called type area, is where a particular rock type, stratigraphic unit, or mineral species is first identified. If the stratigraphic unit in a locality is layered, it is called a stratotype, whereas the standard of reference for unlayered rocks is the type locality. The type localities of celadonite are Planitz, Zwickau, Zwickau District, Saxony, Germany; Malga Canalece-San Valentino, Brentonico, Trento Province (Trentino), Trentino-Alto Adige (Trentino-South Tyrol), Italy; and Tierno-Besagno, Mori, Trento Province (Trentino), Trentino-Alto Adige (Trentino-South Tyrol), Italy.
The most famous deposit of green earth was found near Verona, Italy, and this mine was active until World War II. Other mines produced variations in color and texture of the pigment, such as in the Baltic states, Bohemia, Cyprus, France, Hungary, Poland, Saxony, Tyrol, and the Mendip hills of England. Our green earth is from mines near Mt. Baldo, Italy.Preparation and Alteration
Glauconite is not found in nature as significant accumulations but in combination with clay or sand. Its content rarely exceeds 50% of the deposit, making it necessary to process the mineral as a pigment. The preparation of glauconite is usually done with levigation, sifting, and sometimes electromagnetic separation. Sometimes clay or sandy minerals, tinted with aniline red or copper pigments, have been marketed under the guise of glauconite. Ethyl alcohol can detect the presence of aniline red while mixing a sample with ammonium hydroxide can reveal the presence of copper-based colors.Use in Painting
Medieval artists often used green earth pigments for flesh undertones. This green underpainting neutralized the effect of the pinks and reds of the flesh colors. On the color wheel, the hue of green earth is the approximate complement to the pink used by medieval painters. Complementary colors neutralize each other, and this neutralization was important for medieval painters because of the materials they worked with. Paint pink and red tones of flesh directly onto white gesso would achieve a "sunburn" effect in the flesh of the figures. Painters painted a layer of green earth under the pink to neutralize the pink. The light would pierce the pink layer, then the green, and reach the white. White reflects all light colors, so the paint reflects the light. Each color paint absorbed some colors, or wavelengths, of the light. Thus, as the light passed back through the paint to the viewer, the flesh tones appeared neutral.Permanence and Compatibility
Earth pigments, and green earth, are often described as the most permanent of colors. Green earth is not affected by sunlight or by atmospheric conditions. They do not react with solvents, but according to Feller, green earth is partially soluble in acids and alkalies.Oil Absorption and Grinding
Green earth has good tinting strength and covering power, and the pigment is easily ground. Since it contains some clay, green earth absorbs oil at a moderate to high rate.Toxicity
The pigment is considered non-toxic, but care should always be exercised when handling the dry powder pigment to avoid inhaling the dust.
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Rublev Colours Verona Green Earth Pigment
|Pigment Classification:||Natural Inorganic|
|Colour Index:||Pigment Green 23 (77009)|
|Chemical Name:||Phyllosilicate mineral|
|CAS No.:||Not Listed|
|Particle Size (mean):||12 microns|
|Refractive Index:||nα=1.606–1.625; nβ=1.630–1.662; nγ=1.579–1.661|
|Oil Absorption:||40 grams oil / 100 grams pigment|
|Health and Safety||No acute or known chronic health hazards are associated with this product's anticipated use (most chemicals are not thoroughly tested for chronic toxicity). Protect yourself against potentially unknown chronic hazards of this and other chemical products by keeping them out of your body. Do this by avoiding ingestion, excessive skin contact, and inhaling spraying mists, sanding dust, and vapors from heating. Conforms to ASTM D-4236.|
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