Flint clays

Acid refractory materials include fireclays, flint clays, china clays (kaolins), silica, flint, chalcedony, ganister and titanium dioxide. 

Flint clays and other related rocks are another potential lithium source. These are high alumina clays that are composed largely of we11-crysta11i2ed kaolinite [1318-74-1] and are used for the manufacture of refractories (qv). The lithium content ranges from <100 to 5000 ppm. Deposits occur in many states, including Missouri, Peimsylvania, and Ohio. Lithium (at ca 1.3%) is present in a chlorite mineral that is similar to cookeite [1302-92-7]. High lithium contents may be the reason why some deposits are unsatisfactory for refractory use. 

Because calcium oxide comprises about 65% of Pordand cement, these plants are frequendy situated near the source of their calcareous material. The requisite silica and alumina may be derived from a clay, shale, or overburden from a limestone quarry. Such materials usually contain some of the required iron oxide, but many plants need to supplement the iron with mill scale, pyrite cinders, or iron ore. Silica may be supplemented by adding sand to the raw mix, whereas alumina can be furnished by bauxites and Al202-rich flint clays. 

High alumina clays refer ia the ceramic iadustries to nodular clays, budey-flint clay, budey and diaspore, gibbsitic or bauxitic kaolins (clays), abrasive clays, and others. Siace the depletion of diaspore varieties ia Missouri and Pennsylvania, most bauxitic kaolin and clay is produced ia Alabama and Arkansas. 

An interesting type of clay used widely in the manufacture of refractories is so-called flint clay, which is very hard and has very slight plasticity even when finely ground. Flint clays are essentially pure, extremely fine-grained kaolinite. In some cases the hardness appears to result from the presence of a small amount of free siUca acting as a cement, whereas in other cases it is the result of an intergrowth of extremely small kaolinite particles. 

Fireclays can be dividea into plastic clays and hard flint clays they may also be classified as to alumina content. Firebricks are usually made of a blended mixture of flint clays and plastic clays which is formed, after mixing with water, to the requirea shape. Some or all of the flint clay may be replaced by highly burned or calcined clay, called... 

Basalt, granite, manganese nodules, shale, flint clay, iron formation materials, phosphate rock, fertilizers Calcareous loam soil, loess, polluted farmland soil, sand soil... 

Emerson, T. E. and Hughes, R. E. (2000). Figurines, flint clay sourcing, the Ozark Highlands, and Cahokian acquisition. American Antiquity 65 79-101. 

Flint clays -lithium m [LITHIUM AND LITHIUM COMPOUNDS] (Vol 15)... 

Clay fuses at from 2800 tit 3200T. tl53fi to 1760 0 the uppet limit being for flint clay and the lower for the plastic form which, due to its cc-mcming qualities, is especially valuable in fire-brick manufacture, Red brick is not suitable for refractory service, nor is insulating brick. There are several fire-clay furnace cements on the market that arc adaptable to monolithic lining. The standard sire of fire-brick and insulating brick is 9 inches by 4i inches by 2i inches 122.9 by 11.4 by 6.4 centimeters). 

Fire clays, ball clays, flint clays are kaolinite-rich clays, usually of the 6-axis disordered variety, which contain a relatively high impurity content. Illite, montmoril-lonite, diaspore, boehmite, quartz, and organic material are the minerals usually associated with these deposits. Few, if any, of the kaolinite minerals in these clays have been concentrated enough to afford meaningful chemical data. 

Moore D. M. and Hughes R. E. (2000) Ordovician and Pennsylvanian berthierine-bearing flint clays. Clays Clay Min. 48, 145-149. 

The principal raw materials are refractory clays (fireclays) flint clays are refractory clays with a hard dense texture consolidated by geological pressure. The main clay mineral is usually kaolinite, and the content of impurities should be lower than 5-6%. 

Flint clays do not slake in water into a plastic mass, and exhibit low firing shrinkage. 

The burning shrinkage in the case of flint clays cannot be entirely attributed to the contraction accompanying vitrification. Considering the purity of these clays it is evident that part of the shrinkage is independent of this factor and must be due to a molecular change of another kind, that peculiar to many typical amorphous... 

Besides the flint clays proper there are certain dense fireclays of feeble initial plasticity which lack the other characteristics of this class of materials. Such a clay... 

Flint clays occur in extensive deposits in the upper Mercer and Middle Kittanning formations of Pennsylvania and Maryland, the Sciotoville in Kentucky and the Lower Kittanning and Upper Freeport in Ohio as well as in the pocket formations of the pre-Pennsylvania limestones, 40 to 140 miles west of St. Louis, Mo., probably of cretaceous origin. The Ohio flint clays as a rule are not equal in refractoriness to the others mentioned for which a softening point of cone 33 to 35 is demanded. 

Plastic Refractory Clays.—Clays combining good plasticity with high refractoriness are not of common occurrence. While there are a number of such deposits in the United States, the majority of these materials show plasticity at the expense of heat-resisting power, that is, they soften at temperatures below that of cone 32. Occasionally they develop in limited quantities as the result of the weathering of flint clay. 

Refractory Clay Products.— From the standpoint of the manufacturer the clay refractories may be subdivided into the following divisions (1) Flint-clay refra-torics (2) siliceous-clay refractories (3) plastic-clay refractories (4) grog refractories. 

Properties of Flint-clay Refractories.—These may be briefly summarized as follows The refractoriness of No. 1 materials as indicated by the softening point is usually not lower than that of cone 31 (about 1,685°C. or 3,065°F.). Kanolt has found the mean melting point of 41 samples of firebrick to be 1,649°C., determined in the Arsem furnace. 

---