Rock crystal

But here the similarity ends. Take the right hand piece of glass, and left a piece of rock crystal. Ordinary glass is quickly heated, and rock crystal and remain cool. This feature of rock crystal known by the Romans. In their homes of the wealthy Romans kept large crystal balls, of which cool hand. Cold rock crystal bears no resemblance to the cold snow or ice. Rock crystal cools gentle, pleasant coolness. Its surface only a few degrees cooler ambient air, and therefore does not burn his cool in contrast to the ice. Why is this happening? Rock crystal is much better conductor of heat than glass. Therefore, the warmth of the hands quickly diverges around the stone and the glass is heated only by its surface. Not for nothing that the famous Roman naturalist Pliny - Senior wrote about the rock crystal: "from heaven, Noah moisture and pure white snow hrustali be born." But the famous Roman was a little wrong. Rock crystal - a transparent, clear crystal variety of quartz, of a mineral that is found in the grains of our sands, and a gray translucent stone of our granites, but is in a regular sharpening whetstone, and a colorful agate or yamshe. Clean and transparent crystals of rock crystal reach huge sizes, and samples of 15-20 kilos are not uncommon. On the island of Madagascar have found a rhinestone weighing half a ton. In Switzerland it is mined in large caves. Clean and transparent rock-crystal has long made it an excellent material for cutting or cooking seals and various trinkets. Long time not been able to grow a rhinestone in the laboratory. But about forty years ago in Italy have found a clue, and in very difficult circumstances and in special molds have grown small crystals of rock crystal.