It has become interesting for people to mine semi-precious stones ever since primitive man raised the first colored pebble in the mountains or found transparent amber on the shore.
Types of deposits
Most often, precious stones are mined underground, in mine workings, less often in open pits. It also happens that, under the influence of erosion, stones are gradually freed from the parent rock and are carried downstream by streams of water. In such places, the development of these placer deposits is carried out by manual flushing, using dredges.
On the territory of modern Afghanistan, lapis lazuli mines existed 6 thousand years ago, and the famous traveler Marco Polo wrote about this. Persian turquoise, which is recognized as the best, is brought from Iran. Loose deposits are more profitable than mining ones. Sapphires, rubies and spinels are mined in this way in Sri Lanka, diamonds in Namibia, and amber on the Baltic coast. But the stones in the placers are not of the best quality, since they are rolled, abraded and damaged in other ways over many kilometers of their way from the original deposit.
There are often cases when boulders, inconspicuous at first glance, are hollow from the inside and completely lined with crystals. Such stones are called geodes, and the stones found in them are always better than others in purity and quality. More often than others, amethysts and citrines are found in geodes.
Production methods
At present, scientists are beginning to extract jewelry, who study the origin of rocks and analyze their contents.
After exploration is carried out on the ground and samples are taken from the drilled wells, it is calculated how much material can be extracted in the developed field. After that, the place is considered explored, you can start work.
In African and Asian countries, all stones, with the exception of diamonds, are mined in a primitive way. In the beds of dried up rivers, crevices of rocks and on the coast near the surf, the simplest type of collection is applicable - from the surface of the earth. Often, crystals are knocked off the rocks with the use of jackhammers, blasting. In rivers, the soil is washed in devices like baskets, but light stones, such as tourmaline, quartz and beryl, can be lost at the same time - they are mainly extracted from the primary deposit.
Placers, formed in ancient times, are covered with multi-meter layers of soil, which are removed manually or mechanically, opening the deposit. At the same time, a lot of unusual equipment is used: earth-moving machines that cut the soil themselves and transport it to dumps (scrapers), conveyor-type loaders, machines with buckets suspended from an arrow (draglines). To remove waste rock from open pits, not only dump trucks with conveyors are used, but in some cases also water supplied under high pressure.
