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K15(Fe,Mg,Al)4-6(Si,Al)8O20(OH)4 A type of clay mineral; it is dioctohedral and occurs in flakes and as pigmentary material.



a mineral, hydrated iron aluminosilicate belonging to the hydromica group. It is characterized by variable and complex chemical composition; its main components are silica (49-56 percent), ferrous and ferric oxides (up to 21 percent), aluminum oxide (up to 18 percent), potassium oxide (up to 10 percent), magnesium oxide (up to 7 percent), and water (up to 13 percent). It crystallizes in the monoclinic system.

The color of glauconite is green (from dark green, almost black, to olive green). Its hardness on the mineralogical scale is 2-3, and its density is 2,200-2,300 kg/m3. Its capacity for absorbing water, as well as for ion exchange, is considerable. It is found among sedimentary rocks as round grains of cryp-tocrystalline structure, less frequently as small crystals of roughly hexagonal shape. It is formed at the bottom of the sea, where it settles as a gel. Cases of the formation of glauconite through the substitution of grains of biotite and other minerals in marine ooze are known. Glauconite is widespread in sedimentary rocks of various ages, mainly Mesozoic and Cenozoic.

Because of its capacity for cation exchange, glauconite is used to soften water and, since it contains a considerable amount of potassium oxide, as a soil fertilizer. It is also used for making green paint.

References in periodicals archive ?
13]C in the glauconitic beds in the lowermost part of the Ordovician sections in the Siljan district and on Oland presumably can be correlated with the LTNICE.
II][alpha]) of glauconitic limestone is characterized by the occurrence of Megistaspis planilimbata, M.
A few hundred meters downstream, below the mouth of Little Piney Creek, the glauconitic sandstone of the lower portion of the Reklaw Formation (Newby member) is exposed in the right bank of the river (Locality 6).
The new borehole record may not be that helpful, however, because the waning years of the Cretaceous are represented by glauconitic clay, says Gerta Keller of Princeton University The presence of this clay indicates that the New Jersey site was in shallow water at the time of the impact and thus subject to waves that agitated the seafloor sediments.
PrimeWest's Southeast Alberta Shallow Gas Play consists of shallow gas pools in the Medicine Hat and Milk River formations plus deeper, more prolific pools in Glauconitic zones.
Leoniorthis rubeli occurs in lithologically different more or less glauconitic carbonates with marl or clay interlayers (Meidla 1997).
It belongs to the Turisalu Formation and is overlain by glauconitic sandstones and clays of the Varangu Stage and underlain by the phosphatic quartzose sandstone of the Kallavere Formation [1].
In the main part, the rocks of the Leetse Formation are represented by loose glauconitic silt- and sandstones, resting on the claystones of the Varangu Formation, or (with a hiatus) directly on the graptolite argillites (black shale) of the Turisalu Formation, and overlain by glauconitic carbonate rocks of the Toila Formation.
The first well at Gadsby was drill-stem tested; the Glauconitic flowed gas to surface at a rate of approximately 300 Mcf/d.