Nicosia Green Earth is the natural mineral glauconite, a greenish mineral of hydrated iron potassium silicate containing small amounts of aluminum, calcium, magnesium, sodium, and numerous trace elements. It is a bright green mineral that looks like tiny flakes of the mineral mica or small lumps of clay. The color of glauconite varies considerably from pale green, bright green, bluish-green, olive green, and black-green, depending upon its constituent elements. Our Nicosia green earth is from deposits in southeastern Cyprus near the region of its capital city, Nicosia.
| Pigment Names | |||||||
| Common Names (mineral): | English: glauconite French: glauconite German: Glauconit, Glaukonit Italian: glauconita Spanish: glauconita | ||||||
| Common Names (pigment): | English: green earth French: terre verte German: Grünerde Italian: terre verde Spanish: terra verde | ||||||
| Nomenclature: |
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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.
SourceGreen 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.
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: Baltic states, Bohemia, Cyprus, France, Hungary, Poland, Saxony, Tyrol, and the Mendip hills of England. Our green earth is from Cyprus, where well-known glauconite deposits are found today.
Preparation and AlterationGlauconite is not found in nature as large 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.
Permanence and CompatibilityEarth pigments, particularly green earth, are often described as the most permanent of colors. Earth pigments are 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 GrindingGreen 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 a high rate.
ToxicityThe 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 Nicosia Green Earth Pigment
| Pigment Information | |
| Color: | Green |
| Pigment Classification: | Natural Inorganic |
| Colour Index: | Pigment Green 23 (77009) |
| Chemical Name: | Hydrated Iron Potassium Silicate |
| Chemical Formula: | (K,Na)(Fe3,Al,Mg)2(Si,Al)4O10(OH)2 |
| CAS No.: | Not Listed |
| Series No.: | 3 |
| ASTM Lightfastness | |
| Acrylic: | I |
| Oil: | I |
| Watercolor: | Not Listed |
| Physical Properties | |
| Particle Size (mean): | 10 microns |
| Density: | 2.2–2.9 g/cm3 |
| Hardness: | 2.4–2.9 |
| Refractive Index: | =α1.592–1.610, β=1.614–1.641, γ=1.614–1.641 |
| Oil Absorption: | 42 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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