Ruby (from the Latin ruber "red") is a red gemstone, a variety of the mineral corundum which the color is caused mainly by chromium. Natural rubies are exceptionally rare, while artificially manufactured ones are relatively cheap. In addition to the bright precious stone ruby is also the less bright gemstone of the same name. This stone has been used since ancient times appreciated. The oldest written sources on the extraction of rubies are reporting grooves in Burma. Hence came the stones via trade routes to the courts and to the temples of the ancient Egyptians and Greeks. In the Middle Ages, rubies were also popular in Rome. Initially they were crafted into an oval shape. The very large and beautiful stone also have their own names. The ruby was regarded as the living stone, which strengthens the heart and strength returns. In antiquity and the Middle Ages were known to rubies magical powers. In the Bible, the value of the ruby also recognized, though it is in some of these passages point is that there are treasures of greater value: the wisdom is more precious than rubies (Proverbs 3:15) and the value of a good wife is that of rubies in the eyes of her husband far above (Proverbs 31). In Job 28 ruby is mentioned as one of the treasures that we seek in places where the priceless and impressing wisdom of the living God is not to be found. It should be considered that what is sometimes identified in the KJV as "ruby" in some translations under very different designations emerges. One needs to take into account what this interpretation in the culture and the time of the drafting of the relevant translation was regarded as valuable. Ruby also has mythological significance. Ruby is one of the "nine gems" in Thai Order of the Nine Gems. Rubies are mined in Africa, Asia and Australia. They are most commonly found in Burma, Sri Lanka and Thailand, although they are also found in Montana and South Carolina. Rubies have a hardness of 9 on the Mohs hardness scale, and are among the natural gems in hardness only surpassed by diamonds. Other varieties of corundum are called sapphire. Ruby gemstones are valued according to several characteristics such as size, color, clarity and cut. All natural rubies have imperfections and only artificial rubies may be completely free of imperfections. The fewer the number and less obvious the imperfections, the more valuable the ruby is, unless there are no imperfections (ie, a "perfect" ruby). In that case, could be the fact that it is an artificial ruby. At some artificial rubies added substances so that they can be identified as artificial, but most require the intervention of a specialized appraiser in order to determine the exact value.
Silver has been used for the beginning of our era decorations and cards. Excavations show that already 4000-3500 BC. silver was separated from lead on islands in the Aegean and Anatolia. Silver was often associated with the moon, the sea and various deities. The alchemy was used for silver symbol of a crescent and alchemists called Luna. Metal mercury was thought that it was some kind of silver. In some languages, there is still the name that mercury like quicksilver in English or mercury (meaning alive silver) in older Dutch. Much later turned out to be two completely different elements. The name Silver leads through the Old High German silbar of the Germanic root * seluƀra-. One suspects that it is a loan word that from Asia Minor or even further afield comes here. In Latin it is called Silver argentum, where silver symbol Ag owes. There are at least fourteen languages in which the same word is used for silver and money. Well known examples are the Spanish and French plata argent. Until well into the 20th century coinage of silver and gold, the main payment of humanity. Today we see the use of silver only on commemorative coins and other collector coins and medals. Silver is a widely used material in the applied arts for the production of reliefs, busts, reliquaries, baptismal shells and other liturgical vessels, candlesticks, tobacco and snuff boxes, coffee pots, silverware and other ornamental and utensils. Sterling Silver (alloy with very high silver content) by goldsmiths is widely used for the manufacture of jewelry. Silver bracelets, necklaces and earrings are already known from antiquity. In the 18th century, silver shoe buckles in fashion. A charm bracelet is almost always made of silver. Silver is also used to redeem items made of inferior metals. Silver leaf, consisting of thin slices of silver, is used for decoration, for example in the painting (icons), or gold in the manufacture of leather. A special application of silver leaf is vark (or varakh), India in the popular use to decorate cakes with very thin layers of pure silver. For levels of very high quality silver is suitable because it possesses good light reflecting properties. But usually uses aluminum because it is much cheaper. The good electrical conductivity of silver makes it a very suitable material in electrical and electronic products. In circuits is silver (or silver alloy) used to connect components to each other. For longer connections silver too expensive. As a silver catalyst is used in the industry for example for the production of formaldehyde and ethylene oxide. In dentistry, silver is now no longer used because, while it is relatively easy to make the correct shape, but still has some toxic properties. Because of its disinfectant properties, silver is now also used again to purify drinking water or pure love. Especially for small quantities of water (up to 100 liters) is silver (as silver nitrate), easier to dose and apply than chlorine. In medicine, colloidal silver was once used as an antibiotic, alternative medicine, this happens still. In the laboratory lot of silver nitrate applied as a reagent in chloride provisions, including by precipitation. In addition, the insoluble silver chloride is formed. Silver is used as the silver halides in the photography. Finely atomised silver iodide is used to make rain and to reduce fog around airports. Namely, silver iodide allows for the aggregation of small water droplets which form the cloud. Silver is a metal that is easy to work a little harder than gold and has a white sheen. Silver has the best of all metal electrical conductivity and the lowest contact resistance, better than copper and gold. Gold, by contrast, used more often because it does not corrode. In addition, silver conductive of all metals heat the best and has the highest optical reflectivity (at least as far as the visible light, ultraviolet light reflects the bad). Silver halides are sensitive to light. The metal is stable in pure air and pure water, but when exposed to ozone or hydrogen sulfide discolors it. In the event that silver with sulfur or compounds thereof comes into contact a black layer is formed of silver sulphide.