Glauconite

Glauconite is an iron potassium phyllosilicate (mica group) mineral of characteristic green color with very low weathering resistance and very friable. It crystallizes with a monoclinic geometry. Its name is derived from the Greek glaucos meaning 'blue', referring to the common blue-green color of the mineral; its sheen (mica glimmer) and blue-green color presumably relating to the sea's surface. Its color ranges from olive green, black green to bluish green, and yellowish on exposed surfaces due to oxidation. In the Mohs scale it has hardness of 2. The relative specific gravity range is 2.4 - 2.95. It is normally found in dark green rounded brittle pellets, and with the dimension of a sand grain size. It can be confused with chlorite (also of green color) or with a clay mineral.
Glauconite particles are one of the main components of greensand and glauconitic sandstone, and glauconite has been called a marl in an old and broad sense of that word. Thus references to "greensand marl" sometimes refer specifically to glauconite. The Glauconitic Marl formation is named after it, and there is a Glauconitic Sandstone formation in the Mannville Group of Western Canada.


Physical Properties


Physical Properties of Glauconite

Chemical Classification silicate
Color green, blue green
Streak dull green
Luster earthy to dull
Diaphaneity transparent to translucent
Cleavage perfect
Mohs Hardness 2
Specific Gravity 2.4 to 3.0
Diagnostic Properties color
Chemical Composition (K,Na)(Fe3+,Al,Mg)2((Si,Al)4O10)(OH)2
Crystal System monoclinic
Uses fertilizer, soil amendment

Uses

Glauconite has long been used in Europe as a green pigment for artistic oil paint under the name green earth. One example is its use in Russian "icon paintings", another widespread use was for underpainting of human flesh in medieval painting. It is also found as mineral pigment in wall paintings from the ancient Roman Gaul. Glauconite, a major component of greensand, is also a common source of potassium in plant fertilizers and is also used to adjust soil pH. It is used for soil conditioning in both organic and nonorganic farming, whether as an unprocessed material (for mixing in at proper proportions) or as a feedstock in the synthesis of commercial fertilizer powders.


Sources: Wikipedia

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