China is a significant producer of kaolin with 2.1 Mt in 2002 representing 8.4% of the world's total of 24.9 Mt. The kaolin resources are widespread throughout the country and are varied in their origin, physical and chemical properties and morphology. The kaolin industry, compared to Europe and the USA, is fragmented with no single large company. In 2002, China was the world's largest producer of ceramics, particularly for sanitary ware and porcelain. Also, China is now the second largest producer of paper and paperboard in the world. The quality of kaolin and halloysite is suitable for ceramics with no need to import. However, the quality of existing paper/ board-coating clays is not up to the quality of imported material from Brazil and the USA and there is an urgent need to develop local resources to meet the present and future demands of the market.

The alteration and transformation behaviour of montmorillonite (Wyoming bentonite) was studied experimentally to simulate the mineralogical and chemical reaction of clays in contact with steel in a nuclear waste repository. Batch experiments were conducted at 80 and 300ºC, in low-salinity solutions (NaCl, CaCl2) and in the presence or otherwise of magnetite and hematite, over a period of 9 months. The mineralogical and chemical evolution of the clays was studied by XRD, SEM, transmission Mössbauer spectroscopy and EDS-TEM. Experimental solutions were characterized by ICP-AES and ICP-MS. The main results are that no significant change in the crystal chemistry of the montmorillonite occurred at 80ºC, while at 300ºC, the presence of Fe oxides leads to a partial replacement of montmorillonite by high-charge trioctahedral Fe2+-rich smectite (saponite-like) together with the formation of feldspars, quartz and zeolites.

The adsorption and desorption of Hg(II) by humic acid (HA) previously adsorbed on kaolin was studied. In the range of HA concentration investigated (0.0 –26.9 mg g–1), the Hg(II) adsorption capacity of kaolin at pH 4 is enhanced by the presence of HA. For the complexes with the highest HA concentration and for low Hg(II) initial concentrations, adsorption was lower, i.e. as HA concentration on the complexes increases, Hg(II) equilibrium concentration also increases. This behaviour is due to the increasing presence of dissolved organic matter as the HA concentration on the complexes increases. The dissolved organic matter is able to form a soluble complex with Hg, thus decreasing adsorption. Hg(II) adsorption from a 2.5×10–5 MHg(II) solution was influenced by pH. For kaolin, a pHmax (pH where maximum adsorption occurs) of 4.5 was observed. At pH values >pHmax retention decreased with increasing pH. This same behaviour was observed for the kaolin- HA complex containing the lowest HA concentration (6.6 mg g –1). For the other kaolin-HA complexes there was little effect of pH on Hg(II) adsorption between pH 2.5 and pH 6.5. The presence of HA increased the adsorption of Hg(II) on kaolin all along the pH range studied. Desorption experiments showed that the amount of Hg(II) desorbed was quite low (<1%) for all the HA and Hg(II) concentration range studied, except for the kaolin at acid pH (pH 2.5) where the Hg(II) released was >50% of Hg(II) previously adsorbed. The presence of HA dramatically reduced this percentage of desorption to values of <3%, indicating reduced risk of toxicity problems in surface and subsurface waters. The addition of Cu(II) did not favour any Hg(II) desorption, even though Cu exhibits a strong affinity for organic matter.

A natrolite-cemented palagonite ash tuff unit is reported in a palaeo-basin in northeast Jordan. Phillipsite and chabazite are also identified. The zeolites were formed due to transformation of volcanic glass granules into palagonite by the reaction with percolating water in a closed hydrological system. Consequently, Si, Al, Ca, Na and K are leached out and precipitated in a series of authigenic layers developed at the extreme edge of the granules. The recorded paragenetic sequence is smectite → phillipsite → chabazite → natrolite → analcime → calcite. The natrolite studied is chemically similar to those reported in the literature with minor variations. The phillipsite and chabazite studied are chemically different from the other Jordanian phillipsite and chabazite reported. The latter are chemically equivalent to those formed under open hydrological systems, whereas the phillipsite and chabazite in this study are chemically equivalent to those formed in saline lakes and arid soil environments. This conclusion is based on the (Na+K)/(Na+K+Ca+Mg) ratio and the Si/Al ratio.

Two sedimentary profiles, at 18 km and at 125 km from the Rhône River mouth were selected to study the steps of glauconitization inside green (glaucony) grains, in a temperate marine environment. The proximal site is characterized by a greater content of alpine minerals (chlorite, illite) than the distal one. In the proximal site, pellets at a younger level demonstrate a largely inherited mineral composition. In the older level, representing the most advanced stage of glauconitization, there is a mixed-layer glauconite-nontronite (G-N) phase with 20% glauconite-80% nontronite in dark green grains. In the distal site, more evolved glaucony has up to 92% glauconite in the G-N. In spite of this difference, the glauconitization process developed similarly in the two sites. The relatively low Fe content in the mud-matrix does not reflect the concentration of this element inside the grains. During diagenesis, most of the inherited minerals disappear, making way for neoformed mixed-layer glauconite-nontronite.

The fractal dimension values of several kaolins with different structural order and properties have been calculated from N2-adsorption isotherm data according to the Neimark method. All kaolins show a fractal regime in the same nitrogen relative pressure range, with fractal dimension values ranging between 2.38 and 2.57.

The correlation between fractal dimension and other kaolin characteristics (structural order of kaolinite, BET surface area, brightness and particle-size distribution) was determined. The correlation matrix shows that the fractal dimension (Ds) is highly correlated with the degree of structural order-disorder and is also moderately correlated with the particle-size distribution and brightness. No correlation was observed between BET and Ds, probably because the first is a measurement of the accessible surface while Ds represents the scaling properties of the area.

As Ds is a parameter easily calculated and related to the degree of surface heterogeneity, and well correlated with other kaolinite parameters, it can be used to estimate a set of kaolin technical properties for suitability of the kaolin in the paper industry.

The Fe oxide mineralogy behind the reddish colour (up to Munsell 10R) of a soil and four Quaternary surface deposits from central Jutland (Denmark) was investigated by XRD, TEM, Mo¨ssbauer spectroscopy and bulk saturation magnetization. The red soil (Naesset) consists of a 1 m deep patch, ∼10 m2 in area. It is one of at least 5 –10 isolated spots of limited size which contain hematite and maghemite, and are probably due to local fire.

The four more extended (several hundred m2) red sediments (Salten Skov, Salten, Pot Molle and Laasby) all occur at the feet of slopes and formed from Fe2+-containing seepage water. They contain 25 – ∼100% Fe oxides, originally consisting of ferrihydrite. The well-drained parts of the deposits are at present all dominated by goethite. Hematite and maghemite were also identified at two sites in the top ∼25 cm, one site containing goethite and hematite and probably a little maghemite, and the other goethite and probably hematite. The presence of hematite and particularly maghemite in the surface sediments could be explained by heating of goethite. However, there is no historic or prehistoric evidence of heating activity, and the spatial extension is much wider than that of normal human events. In contrast to the burned soil site, goethite is still present in the upper layers together with a high content of organic matter. Thus, although the present belief is that the deposits formed by heating, site evidence is to the contrary.

Clay mineral analysis of Spodosols collected from the Adirondack Mountains reveals that smectite is common in the forest floor and uppermost soil horizons (the O, A and E horizons) and probably forms from the transformation of vermiculite via a low-charge vermiculite intermediate. The conversion of vermiculite to smectite occurs in the upper part of the soil profile where organic acids and strong inorganic acids (derived from atmospheric deposition) combine to create an intense weathering environment. X-ray diffraction (XRD) and chemical data for the clay fraction indicate that both the smectite and the low-charge vermiculite are Al-rich and dioctahedral. The smectite appears to be a beidellite. Transformation of vermiculite to smectite may have progressed in these acidic horizons by net layer-charge reduction resulting from the progressive substitution of Si for Al. The parent material for the soil clays was probably biotite, but little remains in these soils.