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The unique Lisan soils as engineering materials
Published in P.G. Fookes, R.H.G. Parry, Engineering Characteristics of Arid Soils, 2020
The Lisan soils are found in the Lisan Formation, a sequence of mainly thinly laminated lacustrine deposits laid down within the former Lake Lisan, as described by Begin, Ehrlich and Nathan, 1974. The laminations appear as alternating thin layers of grey silt-size material (calcite) and a white powdery material (aragonite), with thicknesses of laminations down to about one millimetre. Aragonite is the orthorhombic crystal form of calcium carbonate (CaCo3), and weathers to a characteristic white powder.
Natural Materials – Composition and Combinations
Published in Graham A. Ormondroyd, Angela F. Morris, Designing with Natural Materials, 2018
Calcite is the rhombohedral polymorph of calcium carbonate, and is most stable, while aragonite is orthorhombic. Vaterite (hexagonal) is less commonly seen in biomaterials, as it is relatively unstable. In herring, for example, normal mineralisation of the fish otolith is aragonite, but deformed structures with vaterite were shown to be deficient in sodium, strontium and potassium, and can be related to impaired functioning of the inner ear of the fish (Tomas and Geffen 2003). Similarly, low quality pearls with poor lustre were shown to contain vaterite, whereas high quality pearls are almost exclusively aragonite in structure (Ma and Lee 2006). Aragonite is also present in the mother of pearl or nacre found within many mollusc shells (Jacob et al. 2008, Chen et al. 2012). The controlling effect of collagen and the ion concentration of magnesium and calcium has been demonstrated to influence the deposition of calcium carbonate as aragonite or as vaterite in vitro (Jiao et al. 2006) and this may shed light on the control of deposition exhibited in molluscs and sea urchins.
Birefringent Ray Trace
Published in Russell A. Chipman, Wai-Sze Tiffany Lam, Garam Young, Polarized Light and Optical Systems, 2018
Russell A. Chipman, Wai-Sze Tiffany Lam, Garam Young
An example of a non-sequential ray trace in a biaxial crystal involving evanescent waves is considered in this section. Aragonite is a natural form of calcium carbonate CaCO3, different from calcite, which is biaxial with principal indices (1.530, 1.681, 1.685) at 500 nm. Figure 19.34 shows a cube of aragonite with its crystal axes aligned along the edge of the cube. When a laser shines into this cube at a certain range of angles, part of the light will refract into the crystal, then reflect within the crystal, and eventually refract out through the entrance surface. The example ray enters the aragonite block, reflects three times within the crystal, and exits through the front surface. There are four birefringent interfaces along this ray path; thus, a maximum of 24 = 16 modes can potentially exit the front surface. For some incident directions, due to total internal reflections and inhibited reflections, the number of modes decreases. Since the number of exiting modes depends on the crystal axis orientations, ray tracing results will be compared with two sets of crystal axis orientations for the same set of incident rays.
Vipulanandan failure models to predict the tensile strength, compressive modulus, fracture toughness and ultimate shear strength of calcium rocks
Published in International Journal of Geotechnical Engineering, 2021
Limestone is another sedimentary rock, composed mainly of skeletal fragments of marine organisms such as coral, forams and mollusks. Its major materials are the minerals calcite, and aragonite, which are different crystal forms of calcium carbonate (CaCO3) (Abdelaali et al. 2013). Its major materials are the minerals calcite and aragonite, which are different crystal forms of calcium carbonate (CaCO3) (Milliman, Müller, and Förstner 2012). The limestone was popular as a building stone because of its regional availability, its mechanical properties and its attractive appearance, and was used in many types of buildings. Also, limestone has been used in many kinds of constructions such as concrete aggregate, asphalt pavement aggregate, asphalt surface treatments, road base, structural fill, railroad ballast, riprap and drainage and erosion control (Bednarik et al. 2014).
Predicting mechanical properties and ultimate shear strength of gypsum, limestone and sandstone rocks using Vipulanandan models
Published in Geomechanics and Geoengineering, 2020
Wael Mahmood, Ahmed Mohammed, Saman HamaHussein
Limestone is another sedimentary rock, composed mainly of skeletal fragments of marine organisms such as coral, forams and mollusks. Its major materials are the minerals calcite, and aragonite, which are different crystal forms of calcium carbonate (CaCO3) (Rahmouni et al. 2013). Its major materials are the minerals calcite and aragonite, which are different crystal forms of calcium carbonate (CaCO3) (Milliman et al. 2012). The limestone was popular as a building stone because of its regional availability, its mechanical properties, and its attractive appearance, and was used in many types of buildings. Also, limestone has been used in many kinds of constructions such as concrete aggregate, asphalt pavement aggregate, asphalt surface treatments, road base, structural fill, railroad ballast, riprap and drainage and erosion control (Bednarik et al. 2014).
Preparation and characterization of hydroxyapatite from Achatina achatina snail shells: effect of carbonate substitution and trace elements on defluoridation of water
Published in Journal of Asian Ceramic Societies, 2018
Bernard Owusu Asimeng, Joseph Richmond Fianko, Elsie Effah Kaufmann, Elvis Kwason Tiburu, Claude Fiifi Hayford, Prince Atsu Anani, Obed Korshie Dzikunu
XRD patterns obtained for uncalcined and calcined raw shell powders are presented in Figure 1(a) and (b), respectively. The pattern in Figure 1(a) indicates the presence of aragonite in the uncalcined raw shell powders. Aragonite and calcite are two main crystal forms of calcium carbonate. Aragonite is orthorhombic and forms at low temperatures on the surface of minerals whilst calcite has a trigonal crystal structure which evolves at high temperatures. Calcite is more stable and is insoluble at lower temperatures as compared to aragonite. Hence, it is more widely used in HAp synthesis than aragonite [28]. Figure 1(b) shows aragonite transformation to calcite at 700°C through thermal treatment.