Spinel ruby

Rubin, m. ruby, -balas, m. balas ruby (ruby spinel), -blende, /. pyrargyrite. -farbe, /. ruby color, ruby. 

Rubin-schwefel, m. ruby sulfur (realgar), -spinell, m. ruby spinel. 

AB2O4 — Spinel MgAl204-MgCr204, Mg(Alo.99Cr0.0i)2O4 ruby spinel,... 

Spinel (balas ruby, ruby spinel, MgAl204 All colors 3.57-3.72 1.71-1.72 8 One directional poor... 

According to Theophrastus (c. 315 bc), anthrax was a term for ruby or ruby spinel (Hey, 1993 under corundum ). However, Schweppe (1997) points out that in the third century ad Papyrus Graecus Holmiensis (cf. Lagerkrantz, 1913 Reinking, 1925), the harvested, crushed and dried woad (q.v.), was called anthrax. 

Several gemstone species occur in various colors, depending on the presence of impurities or irradiation-induced color centers. Any material can have its color modified by the addition of various impurities synthelic ruby, sapphires, and spinel are produced commercially in over 100 colors. 

CRYSTAL GROWTH FROM THE MELT Vemeuil (flame fusion) ruby, sapphires, and stars spinel rutile strontium [iianale... 

Spinel is found as a metamorphic mineral, and also as a primary mineral in basic rocks, because in such magmas the absence of alkalies prevents the. formation of feldspars, and any alnininnin oxide present will form corundum or combine with magnesia to form spinel. This fact accounts for the finding of both ruby and spinel togedier. 111 addmon to the localities mentioned above, which yield beautiful specimens, spinel is found in Italy and Sweden and in Madagascar, Also in the United States in Orange County, New York, and ill Sussex County. New Jersey, are many well-known spinel localities. Spinel is found also in Macon County, North Carolina, and in Canada in Quebec and Ontario. 

The name spinel is derived from the Greek, meaning a spark, in reference to the fiie-ied coloi of tile soit much used fot gems. Balas ruby is derived from Balascia, the ancient name for Badakhshan, a region of central Asia situated in the upper valley of the Kokcha River, one of the principal tributaries of the Oxus. 

Spinel is a colorless magnesium aluminate (MgAl204) of cubic structure. It is hard and durable, but, like white sapphire, it is not a good diamond substitute because it has a low refractive index and lacks brilliance. However, it is readily doped to produce other gems of various colors. Artificial ruby, for example, is often natural red spinel, and most synthetic blue sapphires on the market are actually blue spinel. 

A number of oxides are economically important ore minerals, such as hematite (iron), chromite (chrome), zincite (zinc), and cassiterite (tin). Some gemstone species are oxides, including corundum (ruby and sapphire), spinel, and chrysoberyl. Corundum is the second hardest natural substance and is used as an abrasive. 

The materials most commonly used as gems and ornamental stones are listed in Table 2.9. This is by no means a complete listing of all materials ever used in jewelry or for decorative purposes. There are many worked specimens that are one-of-a-kind, made from unexpected materials that were opportunistically obtained. These often pose problems of identification and consequently of conservation, since once a stone has been worked it loses its natural luster and form. Stones have been altered with dyes and heat for thousands of years, so it does not hold true that just because something is in an old artifact or Grandma s necklace that it cannot be dyed or otherwise not natural. Synthetics are relatively new, but imitations are as old as the stones themselves. If someone wanted a red gem, and there were no rubies available, then a garnet or spinel could be used instead. No emeralds Use an olivine (peridot) or green sapphire. A synthetic must have the same composition and internal structure as the natural material, but an imitation just has to look like the natural stone. 

Spinel is another simple oxide mineral. It is commonly seen today as a synthetic and may be any color. Natural red spinel was most prized as a gem, and usually was used as an imitation of ruby. Some notable pieces in the British and Russian crown jewels include large uncut spinels. These crystals are a deep red color and are distinctive because of their rough octahedral shape. 

Aluminum, gallium, and thallium form mixed oxides with other metals. First, there are aluminum oxides containing only traces of other metal ions. These include ruby (Cr3+) and blue sapphire (Fe2+, Fe3+, and Ti4+). Synthetic ruby, blue sapphire, and gem-quality corundum are now produced synthetically in large quantities. Second, there are mixed oxides containing macroscopic proportions of other elements, such as spinel (MgAl204) and crysoberyl (BeAl204). 

A nickel-chrome spinel, NiO.CrjOg, has been made artificially in small green crystals. The green colour of emerald, serpentine, possibly sapphire, and other minerals is due to the presence of compounds of chromium, which also occur in rubies, corundums, and spinels. It has been shown that the peculiar spectra of ruby and diamond are due to chromium oxide which has been compelled to vibrate in an abnormal manner, leading to the production of narrow absorption bands. Traces of chromium have been detected in the soot produced by the combustion of coal obtained from deposits at Li ge. Compounds of chromium are not known to play any part in the economy of plants or animals. 

Gemstones Beryllium is also associated with gemstones. A gemstone is a mineral that can be cut and polished for use in jewelry. Some typical gemstones are jade, sapphire, diamond, ruby, amethyst, emerald, spinel, moonstone, topaz, aquamarine, opal, and turquoise. Gemstones are often used as birthstones, which honor the month in which a person is born. (For instance, the birthstone for April is a diamond.)... 

Ruby is a solid solution of a-Al2 03 and Cf203, while spinel in this connection is understood... 

Many famous rubies are in fact spinels, which look like rubies but are far less valuable. Spinels consist primarily of MgAl204, whereas rubies are primarily AI2O3. If the Timur Ruby, a 361-carat spinel, were pure MgAl204, how many moles of MgAl204 would it contain (There are exactly 5 carats per gram.)... 

Fourcroy and Hatiy suggested chromium as a suitable name for the element in recognition of the various colours shown by its derivatives, Greek khroma colour. The same year Vauquelin detected chromium in the spinel ruby while Taessert showed it to be an essential constituent of chrome iron ore or chromite, FeO.Cr2Os — now the main source of chromium compounds. The colour of the ruby is now usually attributed to its chromium content and artificial rubies are manufactured by fusing pure alumina with a little oxide of chromium, to colour it, in an... 

Aluminum oxide (uh-LOO-min-um OK-side) is white crystalline powder that occurs in nature in a variety of minerals, including boehmite, bayerite, corundum, diaspore, and gibb-site. Corundum is second hardest naturally occurring mineral. Only diamond is harder. Aluminum oxide occurs in a variety of chemical forms in a variety of gemstones, including chryso-beryl, ruby, sapphire, and spinel. The color of these gemstones is a result of impurities, such as chromium (in the case of ruby) and iron and titanium (in the case of sapphire). The colors may also vary depending on the kind and amount of each impurity. 

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