Diamond luster

Rutile TiOj is a mineral with a metalhc or diamond luster and a blood-red to yellowish-brown color. The Latin word rutilus just means golden red. Beautiful specimens can be used as jewelry. 

Zircon Figure M30 ZrSiO Tetragonal bipyramidal 4.67 7.5 Yellow, brown, brownish-red. Diamond luster... 

Diamant-glanz, m. adamantine luster, -kitt, m. diamond cement. -mOrser, m, diamond mortar (small steel mortar), -pulver, n. diamond dust, -schwarz, n. diamond black, -spat, m. adamantine spar (corundum). -Stahl, m, very hard steel, tool steel, Diamido-. diamino-, diamido- (see Amido-), -benzol, n. diaminobenzene, -toluol, n. diaminotoluene. 

Glanz, m. luster glitter, polish, gloss glance (in names of minerals) brightness, brilliancy (of diamonds, etc.) water. 

Klein RS, Rubin JB (2004) Immune and nervous system CXCL12 and CXCR4 parallel roles in patterning and plasticity. Trends Immunol 25 306-314 Klein RS, Lin E, Zhang B, Luster AD, ToUett J, Samuel MA, Engle M, Diamond MS (2005) Neuronal CXCLIO directs CD8-t T-ceU recruitment and control of West Nile vims encephah-tis. J Virol 79 11457-11466... 

Pure elemental silicon is a hard, dark gray solid with a metallic luster and with a crystalline structure the same as that of the diamond form of carbon. For this reason, silicon shows many chemical and physical similarities. There is also a brown, powdery form of silicon having a microcrystalline form. The element is prepared commercially by reducing the oxide by reacting it with carbon (as coke) in electric furnaces. On a small scale, silicon has been obtained from the oxide by reduction with aluminum meted. 

Germanium — (Ge, atomic number 32) is a lustrous, hard, silver-white metalloid (m.p. 938 °C), chemically similar to tin. Ge is a low-band-gap - semiconductor that, in its pure state, is crystalline (with the same crystal structure as diamond), brittle, and retains its luster in air at room temperature. Anodic dissolution of the material occurs at potentials more positive than ca. -0.2 V vs SCE. Peaks in the voltammograms of germanium in acidic electrolyte are ascribed to a back-and-forth change between hydrogenated and hydroxy-lated surfaces [i]. Studies are often conducted at p-doped and n-doped Ge electrodes [ii] or at Ge alloys (e.g., GeSe) where photoelectrochemical properties have been of considerable interest [iii]. 

The element crystallizes in a diamond cubic lattice. It is brittle, and has a bright metalhc luster. Ge can absorb H2,02,... 

The luster of a mineral is the appearance of its surface when light is reflected off of it. Minerals can have metallic or nonmetallic luster. Minerals with metallic luster look shiny like a metal. Nonmetallic minerals can have various appearances, such as vitreous (glassy), greasy, silky, brilliant (like a diamond), or pearly. 

Figure 11 shows that the majority of elements, including many main-group ones, are metals. But what exactly is a metal You can often recognize a metal by its shiny appearance, but some nonmetal elements, plastics, and minerals are also shiny. For example, a diamond usually has a brilliant luster. However, diamond is a mineral made entirely of the nonmetal element carbon. 

Talc is one of the softest minerals known. It has a numerical rank of l on the Mohs scale of minerals. The Mohs scale ranks minerals from the softest (1 = talc) to the hardest (10 = diamond). Talc is so soft that it can he scratched with the fingernail. The mineral has a pearly luster and may come in a variety of colors, ranging from white gray, or silver to black, brown, pink, or green. Color variations depend on impurities in the mineral. 

Friable, mirrorlike (when polished) substance with a bluish luster. Insoluble in acids, including HF. Soluble in sodium hydroxide, evolving Hg. M.p. 1423°C, b.p. 2630°C d 2.4. Lamellae or octahedral crystals. Diamond structure. 

Actually, minerals which are transparent transmit light much like glass. These minerals are essentially solids with ionic or covalent bond such as oxides, carbonates, silicates (e.g., calcite, quartz), or native element (e.g., diamond). Minerals which are translucent transmit light on thin edges or in thin section. By contrast, opaque minerals do not transmit light even in thin section and comprise solids with metallic or partially metallic bond characterized by a free electron cloud (i.e., Fermi gas) such as native element (e.g., Cu, Ag, Au), most iron and copper bearing sulfides (e.g., CuS, FeS ), and several transition metal oxides (e.g., Fe, ,. FeTiOj, FeCrp J. As a general rule, all minerals with a metalhc luster are commonly opaque. 

Luster Appearance of a gem s surface in reflected light some gemstones appear vitreous (reflect like glass), pearly, silky, adamantine (refracts light strongly like diamond), and metallic. 

Gemstones must be attractive to viewers. Their attractiveness depends on the color, transparency, and luster of the gem and the way it is cut. The most important gemstones are diamonds, sapphires, rubies, and emeralds. Diamonds are often yellowish and transparent, with a hriUiant adamantine luster. Some of the most valuable diamonds, however, contain more intense green, red, blue, or black colors their rarity often makes them more valuable. 

The cost of gemstones is driven by supply and demand. The most desirable gemstones—diamonds, rubies, emeralds, and sapphires—have the highest cost per carat. The price of a particular gemstone depends on the rarity of its color, its luster, the number of imperfections, and the desirability of its cut. The revenue from diamonds accounts for about 90 percent of that from aU gemstones. 

Germanium is a hard, grayish white element with metallic luster but without the duc-tihty that is typical for most metals. It has the same crystal structure as diamond and is hard and brittle. Chemically, it has many similarities with silicon. Physically, it is mainly characterized by its semiconducting properties. Curiously enough the metal is transparent to infrared radiation of wavelengths 2-16 pm. 

Arsenic, selenium, tin, antimony, and tellurium all exist in metallic and nonmetallic forms. For example, Sn occurs as white tin which has a metallic luster and is a good conductor of heat and electricity, and gray tin in which the atoms are covalently bonded in a diamond-type lattice. Below 18 C, the crystalline white tin slowly changes to the powdery gray tin. This transformation was first observed as blistery outbreaks (called tin pest ) on the surface of tin objects such as organ... 

Observations under the diamond anvil high pressure apparatus strongly suggests that EuO is metallic above 300 kbar and the high pressure phase has a silvery luster (Jayaraman, 1972). The reflectivities of EuTe, EuSe and EuS even up to pressures of 350 kbar do not seem to show any color change which leads to the conclusion that there is no appreciable valence change in them up to 350 kbar. 

Similar qualitative observations with diamond anvil apparatus have shown that Yb monochalcogenides undergo the electronic transition near about 200 kbar pressure (Jayaraman et al., 1974). At high pressures YbS acquires a golden yellow color, YbSe a copperish luster and YbTe a purple color, reminiscent of the changes observed in SmS, SmSe and SmTe at high pressure. In table 20.3 data obtained from pressure experiments are presented. 

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