Is it possible to determine the age of stone?

Typically, the surface of black mud covered with a black crust of gypsum. If a swipe at this crust, it will shatter into tiny needles and sharp stones. In these lanceolate crystallite can see the black stripes. These strips are in the gypsum crust is always horizontally on the same level. It turns out that gypsum crystals grow every year and especially during the summer, usually after the spring floods. At this time the dirty melt water fall into the layer of plaster and remain there as black • strip. Each strip - it is a year of life, annual ring - the kind that can be seen on the cut tree trunk. Deposits of rock salt in the salt lakes, we can calculate the same way. And if sawed pearl, pearl rings, then you can determine the age of this beautiful stone. But there is still more accurate methods of measuring the age of minerals. In most rocks and many minerals containing radium. This is a very rare metal, which itself is formed from other metals. Radium is readily converted into other substances, and especially in the lead. During these transformations of radium released helium gas. These phenomena are millions of years without change. And no heat, no huge pressure did not change the laws of life of these amazing substances. And the more there is in rock radium - the more it turns into lead and helium gas. And to know the specific age of the rock - it is necessary to compare the amount of radium and lead in mining the substance. Since the methods of determining the amount of these substances quite right, we can very accurately estimate the age of various minerals and fossil deposits. The oldest minerals and rocks have an age of between three thousand and four thousand years. Just because a stone was able to restore the chronology of the world.