Haydn H. Murray

Traditional and new applications for kaolin, smectite, and palygorskite: a general overview

Abstract Clays have been and continue to be one of the more important industrial minerals. Clays and clay minerals are widely utilized in many facets of our society. They are important in geology, agriculture, construction, engineering, process industries, and environmental applications. Traditional applications are many. Some of the more important include ceramics, paper, paint, plastics, drilling fluids, foundry bondants, chemical carriers, liquid barriers, decolorization, and catalysis. Research and development activities by clay scientists in academia, government, and industry are continually resulting in new and innovative clay products Many of these new applications are the result of improved processing, which provides clays of higher purity, more precise particle size and distribution, whiter and brighter color, modified surface chemistry, and other physical and chemical modifications. Some new and improved clay products include tailored or engineered paper coating kaolins, enhanced paint thickeners, nanocomposites for plastics, pillared clays as special absorbents and catalysts, clays for liquid fertilizer suspensions, clays for absorption of animal wastes, calcined kaolins with high brightness and low abrasion, faster casting clays, and clays with a very high modulus of rupture. Improvement of mining and processing techniques will lead to the continued growth of traditional clay applications and to the development of new and innovative clay products. Value added products are the wave of the future for the traditional industrial clay minerals.

Mineralogy and geology of the Maungaparerua halloysite deposit in New Zealand

The Maungaparerua halloysite deposit is located on the North Island of New Zealand some 210 km north of Auckland. The halloysite deposit was formed by hydrothermal alteration of rhyolite flow rocks. Superimposed on the hydrothermally altered halloysite is deep intensive surficial weathering resulting from the humid climate on the extreme tip of the North Island. The deposit has been drilled and the cores have been analyzed mineralogically and chemically. Drilling has shown that the deposit is circular or ovate and covers about 350 acres. The altered rocks contain about 50% quartz and fine amorphous silica and 50% of a mix of halloysite, kaolinite, and allophane with a small amount of plagioclase feldspar in the coarse fraction. The upper 8–30m, with an average of 15m, of the halloysite alteration deposit consists of relatively soft clay. Below this soft clay, which is the result of intense surficial weathering, the clay becomes hard and dense. The halloysite and kaolin from this deposit are mined and beneficiated using wet process techniques of dispersion, centrifugation, leaching, dewatering, and drying. The products are used as filler in paper, paint, and plastics and as a ceramic raw material for producing whiteware and fine china. This deposit is unique in that it contains a very high proportion of halloysite in the clay fraction. The detailed geology, mineralogy, geochemistry, and the physical properties of the clay will be discussed.

Clay mineral segregation by flocculation in the Porters Creek Formation

The Porters Creek Formation is mined as an absorbent clay in Illinois, Mississippi, Missouri, and Tennessee. The absorptive properties of the Porters Creek Formation are due to the high content of smectite which constitutes >50% of the minerals present. Analyses of 220 samples of the Porters Creek collected in Illinois, Missouri, and Tennessee indicate that the smectite content is highest on the western side of the Mississippi embayment and that the kaolinite content is highest on the northeastern side. The major influx of detritral clays appears to have entered the embayment from a large river on the northeast side. A major control of the distribution of clay minerals during the time of Porters Creek deposition was differential flocculation of kaolinite, illite, and smectite, as evidenced by the numerous syneresis cracks on bedding planes in the area of greatest kaolinite content. Estimates of the smectite, illite, and kaolinite contents suggest both horizontal and vertical variations among these clay minerals. In certain localities the oxidation of pyrite has created acid conditions, which apparently were conducive to the formation of authigenic halloysite.

Well-ordered kaolinite in siderite concretions from the Brazil Formation, western Indiana

Soft, white kaolinite fills many shrinkage cracks in siderite concretions in shale overlying the Upper Block Coal Member of the Brazil Formation (Pennsylvanian). Initial X-ray powder diffraction (XRD) patterns of this white clay showed that it exhibited an extremely high degree of order. Additional samples of the concretions were collected so that a comparative analysis could be made with the Keokuk, Iowa, kaolinite that is found in geodes (Keller et al., 1966). The Keokuk kaolinite is one of the most well-ordered kaolinites that has been described. The block coal is mined in open pits south of the town of Brazil, Clay County, Indiana. Dark gray to red siderite concretions as large as 50 cm in diameter are relatively common in the shale above the coal. These concretions occur as individual nodules dispersed throughout the shale; some nodules are aligned horizontally along bedding planes in the shale. Many exhibit shrinkage cracks as wide as 8-9 mm which are filled with kaolinite. Sphalerite crystals are locally present in the interior of the concretions and kaolinite is present in shrinkage cracks.

Chapter 10 - Overview of Chinese Palygorskite Clay Resources—Their Geology, Mineralogy, Depositional Environment, Applications and Processing

Chinese palygorskite deposits are discussed in this chapter based on the mineralogy, depositional environment, processes and applications. Chinese palygorskite clays were formed during Miocene. Their mineralogy is very similar to that in the Quincy deposit, Florida, USA. The major mineral is palygorskite which varies from around 55% to more than 90%. Montmorillonite is the second most common mineral, ranging from less than 10% to more than 80%. Quartz is present in all samples, ranging from less than 1% to more than 8%. Other minerals that occur in minor amounts in the samples include sepiolite, illite, dolomite and opal. Both major and trace elements imply that the source material of the Chinese palygorskite is basalt, or basaltic volcanic ash. The overall depositional system is fluvial–lacustrine, which was interrupted by volcanic events. The originally deposited material (volcanic ash) has undergone alteration or transformation. It is suggested in this chapter that basalt was transferred in situ to both smectite and palygorskite. Chinese palygorskite can be processed to both gelling grade and absorbent grade for various applications. The quality of Chinese palygorskite clays is comparable to the world class deposit along the border between Florida and Georgia, USA.

Industrial Minerals--Key to Economic Development

Industrial or non-metallic minerals are essential to economic development. The value of industrial mineral production in the United States is more than three times the value of metallic mineral production. In the developed countries of the world the value of non-metallic mineral production exceeds the value of metallic mineral production. The development of a modern industrialized society requires quality and reasonably priced industrial minerals in such industries as smelting of copper and iron, manufacturing cement, drilling oil wells, manufacturing ceramic materials, and a host of others. Because transportation costs are high most industrial minerals are not imported, so a country or region must have a good raw material source.