Quartz silt

Schieber L, Krinsley D., and Riciputi L. (2000) Diagenetic origin of quartz silt in mudstones and implications for silica cycling. Nature 406, 981-985. 

The difficulties imposed by clay coatings on quartz nucleation probably explain why there are few reports of quartz cementation in shales. The oxygen in quartz silt is isotopically heavy (8 0 = 19%o) compared to sand-size quartz (5 0 = 14%o) (Blatt, 1987) suggesting that a substantial component of relatively low-temperature quartz resides in shales. The application of cathodoluminescence microscopy to shales has been quite limited. In Frio Formation shales of south Texas no convincing quartz cement is observed across a range of depths in which quartz cementation becomes important in associated... 

Milliken K. L. (1994a) Cathodoluminescent textures and the origin of quartz silt in Oligocene mudrocks. South Texas. J. Sedim. Res. 64A, 567-571. 

The black layer is a 3.5 cm thick, black to very dark gray clayey silt with weak lamination. The most notable feature of this layer is the abundance of euhedral, starburst shaped Mn oxide minerals that average 0.5 to 0.1 mm in diameter (Figs. 4E and 4F). The detrital component of this unit is dominated by quartz silt. The upper contact of this unit is slightly eroded and marked by clay clasts and a transition to red laminated clay. 

The phosphorites consist of carbonate-fluorapatite mixed with varying amounts of quartz silt, clay minerals, calcite, dolomite, chert and carbonaceous matter. Most of the phosphate occurs as pellets with amounts of oolites, intraclasts, scales, phosphatic shells and replaced skeletal grains. The pellets are cemented with dolomite, calcite, phosphate or, rarely, chert. Some phosphorite beds are composed of phosphate mud. There is a general decrease in size and abundance of intraclast fragments and an increase in carbonaceous content in the phosphorite beds toward the west. These characteristics, plus the close association of phosphorites with cherts and... 

In practice, evaluating the wettability of a soil is far more uncertain, because soil is a mixture of gravel, sand, silt, and clay particles, as well as other chemical precipitates. The mineral components of soil particles include quartz, feldspar, carbonates, and clay. These components have different wettability by water and oil. Therefore, the retention of oil or water in a soil matrix is heterogeneous and variable. The general wettability of soil or liquid retention in a soil is reported on a statistical basis. 

The finest particles composed of fine silt and clay are carried over much larger distances (Fig. 1.6). Using oxygen isotopes of aeolian quartz, it has been shown that significant quantities of dust with an average diameter of 1-10 microns are transported by jet streams from desert zones over the rest of the world. Eolian admixtures have been referred to explain the presence of Si02 in soils developed in non-quartz-containing volcanic rocks in Hawaii and Israel. 

Properties and extraction processes Oil-sand or tar-sand deposits are naturally occurring mixtures of quartz sand, silt and clay, water and natural bitumen (also called crude or natural bitumen), along with minor amounts of other minerals. Each particle of oil sand is coated with a layer of water, which is surrounded by a thin film of bitumen. 

Rivers transport clay minerals primarily as part of their suspended load (silts and clays). The silt-size fraction is composed of quartz, feldspars, carbonates, and polycrystalline rocks. The clay-sized fraction is dominated by the clay minerals illite, kaolinite, chlorite, and montmorillonite. In addition to suspended particles, rivers carry as a bed load larger size fractions. The bed load constitutes only 10% of the total river load of particles and is predominantly quartz and feldspar sands. 

Silica minerals are a primary mineral classified as tectosilicates, characterized by repeating SiO units in a framelike stracture. Quartz, one of the most abundant minerals on earth, often comprises up to 95% of aU sand and silt fractions. It therefore is representative of the structure and properties of sihca minerals. 

Much of the quartz in the fly ash originates from the coal as silt- and sand-sized particles, and it remains in the ash because it survives thermal transformation during the combustion process (Helmuth 1987). Small amounts of volatilized Si may also oxidize to form very fine crystals of quartz within the fly ash glass (Diamond 1984 Hubbard et al. 1984). Although bituminous coal ash may contain more than 50 wt% analytical Si02, only 5-10 wt% of it is present in the form of quartz (McCarthy et al. 1990). Some Si is present in the mineral mullite, but the majority of it is in the amorphous glass phase. 

In Table 3, susceptibility to weathering increases down the list as fewer silicon-oxygen bonds need to be broken to release silicate. Consequently, quartz and feldspars especially, but also mica in temperate soils, are common inherited minerals in the coarse particle size fractions of soil (the silt and sand fractions, 0.002-2 mm). The amphiboles, pyroxenes, and olivine are much more easily weathered. Thus, soils derived from parent material with rock containing a predominance of framework silicates e.g. granite, sandstone) tend to be more sandy, while those derived from rocks containing the more easily weathered minerals tend to be more clayey. 

Adsorption of Lead from Solution on the Quartz- and Feldspar-Containing Silt Fraction of a Natural Streambed Sediment... 

Adsorption experiments were carried out using only the silt fraction because this fraction lends itself to batch experiments and is similar in composition to the sand fraction, consisting primarily of quartz and feldspar. Furthermore, it was felt that the application of double-layer theories of adsorption would be less appropriate on the clay fraction, where the effects of valence deficiencies resulting from isomorphic substitution in actual clays are probably more important. 

The X-ray diffraction patterns for the sand and silt fractions had a nearly identical predominance of quartz and feldspar peaks. The "clay" fraction, however, showed X-ray peaks from quartz and feldspars as well as for chlorite/montmorillonite. Our use of the silt fraction in the following adsorption experiments is supported by the similarity in composition (i.e., mostly quartz and feldspars and no clays) between the silt and sand fractions. The silt fraction, more easily suspended than sand, was an indicator of the adsorption characteristics that might logically be expected of the sand fraction as well. 

Figure 13 Quartz on silt grains in Wilcox Formation shale, Eocene, Texas Gulf Coast (a) secondary electron image and (b) panchromatic cathodoluminescence image.

Reddish brown (SYR 3/6 to 5/8) sediments are present almost throughout Level C, mostly in the epiphreatic passage (Fig. 5) but also within the enlarged joint that extends upwards beyond the flat roof. The sediments are highly uniform, and consist of abundant angular silt-sized quartz in a reddish clay matrix. Laser particle size analyses of sediment from Bone Chamber (Fig. 6) show that the grain size distribution is polymodal the coarsest grain size (medium-coarse silt) comprises only a small proportion of the... 

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