Glauconites

A number of people have compiled data on the range and average composition of glauconite (Hendricks and Ross, 1941 Smulikowski, 1954 Borchert and Braun,1963). For the present review 69 analyses and 82 structural formulas from the literature were selected. 

It is interesting to compare the average formulas obtained during two previous studies and the present one  

Even though the three calculations have a number of analyses in common, the similarity is more than one might expect. The slightly lower interlayer ion content in the present average formula is probably due to the inclusion of more lMd glauconites 

Statistical data on composition of sixty-nine glauconites 

Variable Mean SE Standard SE Skewness Kurtosis Range 

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K2SO-2 MgSO, and halite and (5) kainite ore, kainite [1318-72-5] 4(KC1 MgSO -11H20, and halite. More than 90% of the estimated potassium reserves occur principally as sylvinite and camaUitite (107). Sylvite, the richest of the minerals at 63% K2O, is the principal economically exploitable reserve. In addition, there are four principal insoluble potassium sUicate minerals, glauconite, leucite, nepheline, and orthoclase—sanidine which range in K2O content from 7 to 22%. These minerals are plentihil but for economic reasons may never be exploited for potassium. 

Phosphorites and Glauconite. Phosphorites, or marine apatites, Ca (F,Cl, OH,l/2C02)(P0 2 commonly, though not predominantiy,... 

Table 4. Chemical Analysis of Illite, Glauconite, and Attapulgite, wt %...

Glauconite. Glauconite [1317-57-3] (123—126) is a green, dioctahedral, micaceous clay rich in ferric iron and potassium. The generally accepted formula for glauconite is (Na,K)Q yg(Fe " oi o 45 o 65 35) io( )2 Glauconite has many characteristics common to iUite, but much... 

Celadonite [71606-04-7] is an iron-rich dioctahedral micaceous mineral that is similar to glauconite. Celadonite has a composition of (Na,K)Q... 

Distinctions between glauconite and celadonite may be vague in the area of approximately 0.2% tetrahedral Al. Celadonite is found as an alteration mineral in mafic volcanic rocks (127). 

Chemogenic Volcanogenic Polygenic <10 >50 <10 Iron-manganese nodules, glauconite, phosphorite, nodules, phUlipsite, palagonite, celestobarite, and evaporites Pyroclastic material 38 Red clay... 

Krajewski, K. P. (1984). Early diagenetic phosphate cements in the albian condensed glauconitic limestone of the Tatra mountains. Western Carpathians. Chemical Abstracts, 10, 114382. 

The Nishikurosawa Formation is composed of siltstone, mudstone, conglomerate and sandstone. Siltstone and mudstone contain foraminiferal fossil such as Globorotalia birnageae, and G. denseconnexa, indicating Zone N. 9 by Blow (1969). The upper part is characterized by glauconite-bearing sedimentary rock. The total thickness is about 150 m. 

Green earth, best known by the Italian name terra verte, is probably the main green pigment not derived from copper. Terra verte is a mixture of two minerals, caledonite and glauconite, both complex silicates of aluminum, calcium, iron, magnesium, and potassium silicate (Grissom 1986). 

Cretaceous sedimentation started with the deposition of fresh-water limestones (Hauterivian) followed by successive layers of marine limestones (Barremian), marls (Aptian), marine limestones (Aptian), glauconitic sandstone (Aptian-Albian) and ended with a package of red detritic deposits. 

Other resolubilized trace metals precipitate as replacement ions in existing solids such as fecal pellets and bone. Examples of these fiassilized materials include barite, phosphorite, and glauconite. These precipitates contain small amounts of a variety of trace metals as well as other elements. As a result, their chemical composition is variable and their structure is usually amorphous, making it difficult to assign them an empirical formifia. 

Sediments formed by the abiogenic precipitation of solutes from seawater are termed hydrogenous. Unequivocal examples of hydrogenous sediments are ones formed from the evaporation of seawater. The minerals deposited are collectively called evaporites and are the subject of Chapter 17. Others form with the assistance, to varying degrees, of marine microbes. For example, bacteria seem to play a role in the formation of Fe-Mn nodules and crusts. Some hydrogenous minerals, such as barite, celestite, glauconite, and francolite, are produced from the precipitation of elements... 

Over longer time scales, clay minerals can undergo more extensive reactions. For example, fossilization of fecal pellets in contact with a mixture of clay minerals and iron oxides produces an iron- and potassium-rich, mixed-layer clay called glauconite. This mineral is a common component of continental shelf sediments. Another example of an authigenic reaction is called reverse weathering. In this process, clay minerals react with seawater or porewater via the following general scheme ... 

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