Chalk deposits

Calcium carbonate, available both from natural sources and as precipitated forms (see Calcium compounds), is most useful in coating because of purity and high brightness, ie, 90—95%. Ground carbonates from marble deposits have high purity levels as do the carbonates from some chalk deposits. 

FIGURE 19 Flint tools. Axes, scrapers, and knives. Flint is a hydrated form of ciyp-tociystalline silica that occurs naturally as irregular nodules in chalk deposits. It is colorless and translucent when pure, but opaque and often colored when it contains impurities. When struck, flint breaks with a conchoidal fracture and the fragments formed have smooth, sharp edges. It is for this reason that prehistoric humans used flint to make tools. Since it also sparks when struck, flint was also used, until the eighteenth century, for lighting Are. 

The table shows logarithms of CaCCh-chalk filling weights from two deposits A and B as determined in 11 laboratories with three replications. Use analysis of variance to determine whether there are significant differences between labs or chalk deposits. 

Portland cement is a finely ground, powdered mixture of compounds produced by the high-temperature reaction of lime, silica, alumina, and iron oxide. The lime (CaO) may come from limestone or chalk deposits, and the silica (Si02) and alumina (AI2O3) are often obtained in clays or slags. The blast furnaces of steel mills are a common source of slag, which is a byproduct of the smelting of iron ore. 

Second to water in quantity is chalk exactly the same material that schoolteachers use to write on blackboards. It is collected from the crushed remains of long-dead ocean creatures. In the Cretaceous seas chalk particles served as part of the wickedly sharp outer skeleton that these creatures had to wrap around themselves to keep from getting chomped by all the slightly larger other ocean creatures they met. Their massed graves are our present chalk deposits. 

ODP Site 689 was cored on the eastern flank of Maud Rise in the Weddell Sea (Barker et al. 1988). Hole 689B (64°31.009 S 03°05.996 E) was drilled to 297.3 m. Age control is from foraminifera, nannofossils, diatoms and palaeomagnetics. The Eocene extends from about 130 to 200 mbsf, with a sediment accumulation rate of 4-4.5 m/m.yr. The sediment is described as nannofossil ooze and chalk deposited in a pelagic environment (Barker et al. 1988). 

To determine the optimal amount of sorbent the dependence of the degree of extraction of the cationic blue dye from aqueous solutions on the mass of the sorberrts has been studied. The sorbents are cellulose sorbent (sawdust) and natural mineral (carbonate rocks, chalk deposits of Konyshovka settlement, Kursk region). 

Flint. Nodular chalcedonic silica from the chalk deposits of W Europe and elsewhere. These flint pebbles are calcined and ground for use in earthenware and tile bodies. In USA the term flint is often applied to other finely ground high-silica rocks used in whiteware manufacture. See also... 

Remove loose chalk deposits and apply a new coating system. 

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