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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
Luster refers to the sheen of a mineral, that is, to the way it reflects light; some examples are shown in Figure 3.36. For example, minerals that have the shiny appearance of polished metal are said to have a metallic luster. Most minerals, however, do not have a metallic luster; they have a nonmetallic luster. Mineralogists use many terms to describe nonmetallic minerals. We call those that appear only partially metallic submetallic. Vitreous minerals, like quartz, have a glassy appearance. Adamantine minerals sparkle or appear brilliant like diamonds. Some not-so-spectacular minerals do not have bright or flashy lusters; we may describe them as earthy, dull, or resinous. Some mineral specimens, such as the sphalerite shown in Figure 3.36, may have more than one luster or color depending on how they were formed. Table 3.7 lists some of the more common terms used to describe luster.
Rock Forming Minerals
Published in Aurèle Parriaux, Geology, 2018
The reflectivity of a mineral is the ratio of reflected flux to incident flux. It directly influences the luster of a mineral. Metallic luster (as shown by the sulfides) is distinguished from nonmetallic luster. In the non-metallic category there is vitreous luster (quartz, feldspars), adamantine (diamond), resinous (sulfur, sphalerite), greasy (chalcedony), silky (gypsum), pearly (micas), porcelaneous and earthy (no luster because it is an aggregate of small variously-oriented grains).
The Alloga quarry, Southwestern Sinai, Egypt: geological studies, radioactivity and mineralogical investigations
Published in Egyptian Journal of Basic and Applied Sciences, 2020
Osama R. Sallam, Ahmad M. Abdrabboh, Abd Elhadi A. Abbas, Hani H. Ali, Abdalla S. Alshami
This mineral occurs as granular grains ranging in color from yellow to pale orange with a waxy luster and sometimes presents as prismatic acicular crystals or radial-fibrous aggregates ranging in color from yellow to greenish yellow with vitreous luster (Figure 7). The X-ray diffraction diffractogram (XRD) shows that the separated sklodowskite grains are matching with the ASTM card No. (70–497). The EDX data indicate the presence of U (22.19%), Si (34.17%), Mg (10.55%), Al (23.85%), K (5.58%), Fe (2.06%) and Ca (1.59%).