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The geological origin of building stones
Published in John A. Hudson†, John W. Cosgrove, Understanding Building Stones and Stone Buildings, 2019
John A. Hudson†, John W. Cosgrove
An early definition of a mineral was given by Friedrich Mohs (1773–1839), a German scientist, who defined minerals as ‘inorganic products of nature’. We can amplify this definition to ‘a mineral is a naturally occurring, solid, homogeneous, crystalline, chemical element or compound’. Mohs is most famous for his scale of hardness based on the ability of one mineral to scratch another; it is a measure of the resistance of the mineral to scratching, noting that the hardness of a mineral is mainly controlled by the strength of the bonding between the atoms and the size of the atoms. There are ten minerals in Mohs scale: talc (the softest), then gypsum, calcite, fluorite, apatite, orthoclase, quartz, topaz, corundum and diamond (the hardest), Figure 2.1. The logic of the Mohs scale is that any mineral can scratch any mineral below it on the scale, and conversely can be scratched by any mineral above it.
Isotropic Amorphous Optical Materials
Published in Daniel Malacara-Hernández, Brian J. Thompson, Advanced Optical Instruments and Techniques, 2017
Luis Efrain Regalado, Daniel Malacara-Hernández
The hardness of materials is important: hard materials are more difficult to scratch but also more difficult to polish. The Mohs scale, introduced more than 100 years ago by Friedrich Mohs (1773–1839), is based on which materials scratch others and ranges from 1 to 10, in unequal steps. Table 19.5 shows the materials used to define this scale.
Microstructure and mechanical properties of SiO2-Al2O3-CaO-ZrO2 based glazes containing zircon and diopside phases
Published in Journal of Asian Ceramic Societies, 2023
Figure 7 shows the micro-Vickers hardness results of the glaze samples with various amounts of MgO, sintered at 1230°C. M1 showed a hardness value of 6.23 GPa, where an increase in the amount of MgO resulted in an increase in the hardness. M5 showed the highest hardness value of 7.07 GPa. In particular, it was observed that in M3, where crystallinity rapidly increased and a complex crystal phase with a diopside crystal phase in addition to the zircon crystal phase formed, the hardness of the glaze surface increased rapidly. The hardness of the glaze with complex crystal phases was superior to that of commercial zircon-containing glazes of 5.80 to 6.44 GPa [22,25]. F. Pei. et al. reported an increased diopside crystal phase resulting in increased hardness of the glaze surface when MgO was added to the CaO-Al2O3-SiO2-based glaze [19]. S. Banijanali reported that crystallinity increasing, and residual glass matrix affects the enhancing hardness of glaze [31]. Zhu. et al. reported that as TiO2 of nucleating agent addition increased, the crystalline-phase fraction and hardness enhanced [32]. It is determined that the crystallinity of the glaze increases with the increase in the amount of MgO added and the formation of high-hardness zircon (Mohs scale: 7) and diopside (Mohs scale: 6.5) crystal phases contribute to the enhancement of the hardness of glaze [16,19,25,31].
The effect of vermiculite and quartz in porous concrete on reducing storm-runoff pollution
Published in ISH Journal of Hydraulic Engineering, 2021
Armin Azad, Sayed-Farhad Mousavi, Hojat Karami, Saeed Farzin, Vijay P. Singh
Quartz is a kind of silicon dioxide (silica) and the second most abundant mineral material in the earth’s crust after feldspar. This material is composed of a continuous grid such that each oxygen atom is located between two tetrahedrons. Quartz is a mineral with very high hardness (7 in the Mohs scale). This mineral is resistant to weathering and melts at 1670°C. Its compressive strength is between 1300 and 1600 MPa. In recent years, studies have been done on the ability of quartz to enhance the physical properties of concrete and improve the quality of wastewater (Balabin and Syunyaev 2008; Lian and Zhuge 2010; Van-Wyk and Croucamp 2014; Tufail et al. 2017). The chemical characteristics of the applied quartz are given in Table 1.
Monograph on desilting basins sizes estimation for hydropower projects
Published in International Journal of Green Energy, 2019
Hydropower projects constructed on erosive mountain faces severe issues due to sediment. The sharp-edged quartz sands transported by rivers in hilly terrain causes rapid wear of turbine runner blades/buckets due to abrasion (Sangal, Singhal, and Saini 2018). Hardness of quartz on Mohs scale of hardness is 7 out of a maximum 10. Therefore, the river sediment containing a large percentage of quartz has abrasive action on hydro-mechanical equipment (Asthana 2007). In run-of-river hydel projects, when sediment load (particularly sharp-edged quartz sands) is high, sediment removal may be done by desilting basin (Singh and Kumar 2016). The basic principle for sedimentation is to reduce the velocity of flow by increasing cross-sectional area of conduit so that suspended particle denser than water will settle into the bottom, in flowing water due to force of gravity (Novik et al. 2014). These are removed through flushing arrangement. Once the minimum size of sediment to be excluded has been decided, the design of desilting basin involves the determination of the dimension of the desilting basin and the choice of method for removal of the deposited sediment, i.e., flushing arrangement.