China
Africa
Explore chapters and articles related to this topic
Rocks and rock minerals
Published in Ivan Gratchev, Rock Mechanics Through Project-Based Learning, 2019
During eruption (Figure 4.2a), gas bubbles in the molten lava become voids in the solidified form, producing light and porous volcanic rocks such as pumice and scoria (Figure 4.4). Volcanic glass (also known as obsidian) arises from the sudden cooling of lava droplets during flight.
Minerals
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
Some mineral-like substances, termed mineraloids, are partially or completely amorphous, which means they have a random atomic structure and thus are not crystalline. Some examples are shown in Figure 3.13. For example, natural volcanic glass, called obsidian (top photo), forms so quickly that atoms cannot arrange themselves in a regular, repetitive atomic structure. The process produces a glass that, unlike a mineral, is noncrystalline. So, obsidian is considered a mineraloid.
Isotropic Amorphous Optical Materials
Published in Daniel Malacara-Hernández, Brian J. Thompson, Advanced Optical Instruments and Techniques, 2017
Luis Efrain Regalado, Daniel Malacara-Hernández
Glass is a material in a so-called glassy state, structurally similar to a liquid. At ambient temperatures, it reacts to the impact of force with elastic deformations. Thus, it can be considered as an extremely viscous liquid. It is always an inorganic compound made from sand and sodium and calcium compounds. Plastics, on the other hand, are organic. Glass can also be in natural forms, such as obsidian, found in volcanic places. Obsidian was fashioned into knives, arrowheads, spearheads, and other weapons in ancient times.
Investigation on the Matte/Slag/Spinel/Gas Equilibria in the Cu-Fe-O-S-SiO2-(CaO, Al2O3) system at 1250 °C and pSO2 of 0.25 atm
Published in Mineral Processing and Extractive Metallurgy Review, 2023
Min Chen, Katri Avarmaa, Pekka Taskinen, Radoslaw Michallik, Ari Jokilaakso
To demonstrate the reasons for the differences in iron and sulfur concentrations in matte between the present study and previous works (Fallah-Mehrjardi et al. 2018b; Hidayat et al. 2018; Sineva et al. 2020, 2021a), the total concentrations of trace elements (Ag, Ni, Co, and Sn) in matte in this study were calculated and displayed as a function of matte grade, shown in Figure 4(f). It can be seen that the total concentration of trace elements in matte in this study was approximately 1.5–2 wt% and had no significant changes with increasing matte grade. The deportment of trace elements into the matte phase contributed to the gap between the present study and results from literature (Fallah-Mehrjardi et al. 2018b; Hidayat et al. 2018; Sineva et al. 2020, 2021a). On the other hand, the copper and iron concentrations in matte in the compared studies (Fallah-Mehrjardi et al. 2018b; Hidayat et al. 2018; Sineva et al. 2020, 2021a) were calculated without considering oxygen in matte. They estimated the oxygen concentrations in matte by taking the difference between 100 and the sum of Cu, Fe and S in matte, whereas in the present study, the oxygen concentration in matte was measured and calibrated by obsidian in the EPMA analysis. The different calculation methods for the concentrations of copper, iron, sulfur, and oxygen in matte may also led to the existence of differences between the data.
Formulation and use of manufactured soils: A major use for organic and inorganic wastes
Published in Critical Reviews in Environmental Science and Technology, 2022
R. J. Haynes, Y.-F. Zhou, X. Weng
There are a number of materials derived from volcanic activity that are used particularly in container mixes. These include (a) pumice which is a spongy, porous form of volcanic glass, (b) perlite which is an amorphous volcanic glass formed from hydration of obsidian which when crushed and heat-treated forms an expanded light-weight product and (c) tuff which is a type of igneous rock mined in quarries (Papadopoulos et al., 2008). Vermiculite is also commonly used in container mixes and consists of vermiculite 2:1 clay exfoliated by heating to 1000 °C. Rockwool is manufactured by melting basaltic rock with limestone and coke at high temperatures and spinning the melt into fibers. It is used in horticulture either as rigid slabs, blocks or cubes (especially for glasshouse vegetable production) and as granules for use as a component of container media (Bussell & McKennie, 2004).
Economic geology and genesis of kaolin resources in the East African Rift system: the case of Alemtena kaolin deposit, Ethiopia
Published in Applied Earth Science, 2020
Getnet Gezahegn, Worash Getaneh
According to Ephrem (2010) and Kazmin and Seifemichael (1978), the geology of the MER is grouped into three lithostratigraphic sequences: pre-rift, syn-rift and main rift sequences. The pre-rift units are constituted by Precambrian metamorphic, Mesozoic sedimentary and Oligocene to Late Miocene plateau flood basalts. The syn-rift units are Upper Miocene-Quaternary volcanics constituted by Nazret pyroclastic rocks of welded to partially welded pyroclastic flows and rhyolitic and trachytic lava domes. Syn-rift volcanism has bimodal character with predominant acid products and associated basalts. These units have an age of 8 Ma years (Weldegabriel et al. 1990). Main rift units comprise Quaternary-Holocene young central volcanoes, basaltic and obsidian lava flows, trachyte, rhyolitic domes, and pyroclastic flow and fall deposits. Pyroclastic and pumice fall deposits of Bora-Bericha group in which the current study area is situated is related to the main rift units.