Rublev Colours Tavush Green Earth is the greenish mineral celadonite—s phytosilicate of hydrated iron potassium silicate containing small amounts of aluminum, calcium, magnesium, sodium, and numerous trace elements. It is a green mineral that looks like tiny flakes of the mineral mica, or small lumps of clay. The color of celadonite varies considerably from pale green, bright green, bluish-green, olive-green, and black-green, depending upon its constituent elements. Rublev Colours Tavush Green Earth is from the Idzhevanskoe deposit, Idzhevan, Tuvash province of Armenia.
|Common Names:||English: green earth |
French: terre verte
Italian: terre verde
Spanish: terra verde
|Mineral Names:||English: celdadonite |
The word celadonite is derived from the French word& celadon, meaning sea-green. It has been in painting since ancient times, found recently on Roman frescoes. Restorers have proved through X-ray diffraction that the famous pigments of past centuries known as Veronese terre verte are in essence celadonite minerals.
Celadonite is almost exclusively found associated with basic-eruptive rocks in deep-marine environments. Altered basalts from ocean-bottom environments which contain celadonite have been found. Basalts containing celadonite can, of course, also be found on dry land, but these are usually assumed to have originated from marine environments.
Green earth pigments, also widely known as terre verte, in its dry, powder form is a dull green color. They are inorganic pigment composed of the minerals celadonite and/or glauconite. However, according to Anne Wall Thomas, “Green earth, or terre verte, is a mineral but not in the strictest sense an iron oxide pigment. Consequently, it cannot be classified as a product of one of the four iron ores. 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. The green earths, which contain small amounts of iron along with manganese and other components, may have origins in oceanic deposits.” (Thomas, 12–3)
Anne Wall Thomas (1980) Colors from the earth: The artist's guide to collecting, preparing and using them. Van Nostrand Reinhold Co.Particle Size
The particle size composition of Tavush Green Earth is 80–85% from sub-0 to 15 microns with the remainder ranging up to 30 microns with only 0.1% at 30 microns and above.Permanence and Compatibility
Green Earth is among the most permanent colors among the artists' palette. It is compatible with all other pigments, and can be used with good results in all mediums.Oil Absorption and Grinding
This pigment is easy to grind in vegetable drying oils and water. The oil absorption value (OAV) is 28 grams of linseed oil for 100 grams of pigment.Toxicity
The pigment is considered non-toxic, but care should always be exercised when handling the dry powder pigment so as not to inhale the dust.
Rublev Colours Pigment: Tavush Green Earth
|Color Index:||Pigment Green 23 (77009)|
|Chemical Name:||Hydrated Iron Potassium Silicate|
|Chemical Formula:||KMgFe3+Si4O10(OH)2 |
|ASTM Lightfastness Rating|
|Oil Absorption:||28g oil / 100g pigment|
|Bulk Density:||2.95–3.05 g/cm3|
|Refractive Index:||nα = 1.606–1.625 nβ = 1.630–1.662 nγ = 1.579–1.661|
|Heat Stability:||320° C|
|Silicon Dioxide (SiO2)||63.66|
|Aluminum Oxide (Al2O3)||16.36|
|Titanium Dioxide (TiO2)||0.69|
|Iron Oxide (Fe2O3)||7.08|
|Manganese Oxide (MnO)||0.09|
|Calcium Oxide (CaO)||2.32|
|Magnesium Oxide (MgO)||1.81|
|Chromium Oxide (Cr2O)||–|
|Potassium Nitrate (K2O.N2O3)||5.20|