Rock crystal

Silicon makes up 25.7% of the earth s crust, by weight, and is the second most abundant element, being exceeded only by oxygen. Silicon is not found free in nature, but occurs chiefly as the oxide and as silicates. Sand, quartz, rock crystal, amethyst, agate, flint, jasper, and opal are some of the forms in which the oxide appears. Granite, hornblende, asbestos, feldspar, clay, mica, etc. are but a few of the numerous silicate minerals. 

Rochelle salt, see Potassium sodium tartrate 4-water Rock crystal, see Silicon dioxide Rutile, see Titanium(IV) oxide... 

Quartz. When colorless, quart2 [14808-60-7] is also known as rock crystal. When irradiated, it becomes smoky from a color center associated with a ubiquitous Al impurity at about the 0.01% level. The name citrine [14832-92-9] is used when quart2 is colored by Fe, and irradiation of this can produce the purple-colored amethyst [14832-91-8] under certain circumstances (2). Although not signiftcandy lower priced than the natural materials, synthetic citrine and amethyst ate used in jewelry because of the abiUty to provide matched sets of stones from large, up to 7-kg, hydrothermaHy grown crystals. 

Berg-kalk, m. rock time (Geol.) mountain limestone. -kiesel, m. rock flint, chert felsite. -kohle,/. (mineral) coal, -kork, m. mountain cork (a light form of asbestos), -kreide, /. rock lime, -kristall, -krystall, m. rock crystal (transparent quartz), -kupfer, n. native copper, -lasur, /. azurite. -leder, n. mountain leather (a form of asbestos), -maun, m miner. 

Quarz-keil, m. (Optica) quartz wedge, -kiesel, m. quartz gravel, -kristall, m. quartz crystal, rock crystal. -lager, n. quartz deposit, -linse, /. quartz lens, -mehl, -pulver, n. quartz powder- -rohr, n., -rohre, /. quartz tube, -sand, m. quartz sand, -scheibe, /. 

Silicon Dioxide (Quartz, Lechatelierite, Tri-dymite, Silica, Silicic Anhydride, Rock Crystal, Cristobalite, Sand). Si02, mw 60.08,... 

Rock crystal Vitreous Transparent Colorless Conchoidal fracture... 

Woo l Rock crystal Paper +12 Tufnol PAMA (plasticized)... 

Silicon dioxide (SiO ) is the most abundant compound in the Earths crust. Known as common sand, it also exists in the forms of quartz, rock crystal, amethyst, agate, flint, jasper, and opal. It has many industrial uses. 

Crack Cocaine Street Names Freebase. Mexican speedballs (crack w/ methamphetamine), roosten tornado (ovct 40 street slang terms) Use Crack is cocaine that comes in a rock crystal that can be heated and its vapors smoked. The tOTn crack ref s to the crackling sound heard when it is heated Actions CNS stimulant induces euphoria. Highly addictive Effects Acute CV or cerebrovascular emergencies (heart attack or stroke), could result in sudden death. Cocaine-related deaths are often a result of cardiac arrest or seizure followed by resp arrest (see also Cocaine)... 

Sihca, the other most important class of sihcon compounds, exists as sand, quartz, flint, amethyst, agate, opal, jasper, and rock crystal. It is discussed separately under Sihcon Dioxide. Silicates and silica have many applications... 

Quartz occurs in granite, sand, crystals, and sandstone. Quartz also has several crystalline varieties such as purple amethyst, colorless rock crystal, and yellow citrine. Flint, agate, and chert, etc. are other forms of quartz. Quartz is an excellent insulator. It does not break under temperature changes because of its low coefficient of expansion. Fused quartz transmits ultraviolet light. 

A nice property of isotopes is that when minerals form from a common source such as a magma, all minerals will have identical isotopic ratios (the same as that in the magma) if all isotopes are corrected for mass-dependent isotopic fractionation. That is, if several minerals in a volcanic rock crystallized at roughly the same time (within a day, a month, a year, or 1000 years, depending on the resolution of age determination), they would all have the same " Nd/ " " Nd ratio. Hence, in the above equation, ( " Nd/ " " Nd)o is a constant. Furthermore, for rocks formed at the same time, — 1) is also a constant. Because Sm and Nd have different chemical properties, their concentrations and hence the Sm/ Nd ratio vary from one mineral to another. With different Sm/Nd ratios in different minerals, after some time (such as one billion years), the Nd/ Nd ratio would vary from one mineral to another. Hence, when we measure Nd/ " " Nd... 

The decay of °Th leads to radioisotopes of other elements, ultimately concluding with the stable isotope lead-206. Happily, some of the oldest rocks on Earth, called zircons, contain no lead when they are formed. This means that the amount of lead they accumulate over time from uranium decay reflects their age. Until the rocks crystallized, uranium atoms could move freely through the molten magma from which they formed, and decayed uranium could be replenished. Solidification of a zircon does for uranium what an organism s death does for radiocarbon it stops the influx of fresh radioactive material, and the decay clock starts ticking. Because of U s long half-life, zircons can be dated back to the Earth s earliest days. 

For example, in the lengthy Natural History [2], by the famous Roman natural historian Gains Plinius Secundus, there are descriptions of polyhedral forms of beryl, rock-crystal, diamond, etc. 

Various names, such as amethyst, citrine, and smolqr or black quartz, have been used for colored rock-crystal, whereas for the cryptocrystalline aggregate of quartz, names such as chalcedony and jasper are used. Agate and cornelian, for example, are types of chalcedony that have specific textures or colors. In this chapter, we analyze how a variety of morphologies of high-temperature and low-temperature quartz appear, and how textures of polycrystalline aggregate seen in agate and other crystals are formed. 

Although the principal morphology of rock-crystal is a hexagonal prismatic Habitus, natural crystals may deviate from this. In Goldschmidt s Atlas der Kristallformen (see ref. [1], Chapter 9), 855 crystal figures are compiled in 54 plates. A few examples are shown in Fig. 10.2, in which various forms are observed, such as malformed hexagonal prisms, tapered prisms, platy, and scepter forms. (See also Fig. 1.1.)... 

Figure 10.2. Various forms of rock-crystal. Selected from Atlas der Kristallformen (ref. [1], Chapter 9).

The anisotropy in the growth rates of the s5uithesis of rock-crystal at an industrial scale is depicted in Figure 10.4 [1]. R is the smallest, the order being... 

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