opal mines Dubn�k - located about 30 kilometers from the Slovak town of Pre�ov near the village �ervenica. Dubnick� opal mines were known in the sixteenth century and the discovery of deposits in Mexico and Australia were the largest source of this mineral in the world. Historians do not exclude that opal from this site for people already conquered the Roman Empire.

Dubnick� opal was true in the past term, and it boasted a number of princes and prominent personalities in the whole of Europe.

It is known that he was well liked by the family members of the French Emperor Napoleon: one of these rare stones, called Trojan fire, worn as adornment, Empress Josephine. The largest opal Dubnick� however did not come from the underground: a stone weighing 607 grams was found in 1775 in the local creek. He was named Harlequin (Vienna Imperial Opal) and now it can be admired at the Natural History Museum in Vienna, where it is stored. Reached peak production between 1845-1880, when the tenant became a family Goldschmidt. In this period worked in the mines and more than 350 miners excavated stone processed to thirteen cutters.

In 1896 he took over the mines happen, but even before the First World War (since about 1908) began mining limit. The reason was problems with sales, which culminated when closing down in 1922. The lower demand for Slovak opal was emerging mining in new deposits in Mexico and Australia.

Meaning dubnick�ho opal closer as a book Slovak opal - rediscovery of the king's jewels, which were written by Italian Luigi Constantini gemology.

Opal - The name of this gem apparently comes from the Sanskrit word upala which meant gemstone. It occurs in a variety of color variations. The so-called precious opal is admired for typical optical phenomenon called opalescence, which cause interference of light at the interfaces of submicroscopic layers of gel beads mineral. Opal is hydrated silica (SiO2 � nH2O), without regular crystal structure in some cases can bind up to 20 percent water. It is mainly used as a jewel, but the application is also in the chemical industry, which in some cases is applied as a filter.