Emerald, The May Green

The green colour of emeralds is hard to describe, even if they are full of expression and passion. This green, full of dynamics and one and only depth, have always made a big impression on people. The decisive role in creating that green colour plays chromium oxide. The name emerald belongs only to those beryls, that have chromium and/or vanadium as the staining factor. The intensity of its colour depends on the level of chromium, which can reach as much as a few percent. The trace elements often occurring along the chromium, such as iron and vanadium, are responsible for the yellowish and blueish tints. The most valuable and most beautiful tint is the sharp, fresh green of may grass. Moreover, emerald is one of the few precious stones, that emanate with their shine in darkness, illuminated only with the candles’ light.

The rareness of occurrence of fine coloured emeralds comes from the fact that both of the elements, beryl and chromium almost never occur one beside the other. The emerald, despite its hardness of 7,5 to 8 is less resistant to mechanical stress than other stones of the same degree of hardness. It must therefore be handled with caution. The internal stresses occurring during the growth phase often cause the fine inner cracks, which cause its braking when worn as jewellery. The high prices of these stones, along with their exceptional rarity, make it more likely - comparing to other minerals – for them to be polished even if presenting lower purity. Therefore, the presence of inclusions is also an undeniable proof of the originality of emeralds.

The most decorative of beryls has the same physical properties as the other members of beryl family, but depending on the place of formation, it differs significantly in light refraction and density. According to tradition and the course of events, the emerald - how could it be otherwise in the case of a stone with such challenging colour – it expressed different emotions. In ancient times the name emerald included not only the gem itself, but also any stones of a green colour. Caesar collected emeralds due to the healing effects attributed to them. The Karol the Great’s crown, as well as the famous Iron Lombardy crown were studded, among others, with emeralds. Until the late Middle Ages emeralds were a great rarity and were valued high. All of them came in those times from the two only known deposits: Cleopatra's mine by the Red Sea in the Wadi Sikkat of Egypt and the Habachtal River mine in Austria.

One of the most famous emeralds in history was the Crown of Andes, given by the inhabitants of Popayán city in Colombia to the Holy Virgin Mary the Queen of Andes in gratitude for saving them from the three year plague. Twenty-four goldsmiths worked continuously for six years, to carve delicate and richly decorated crown from a massive lump of gold. This jewel is adorned with 447 emeralds weighing a total of 1524 carats. Neither torture nor fear of death have been able to take away the secret from the Inca priests about their source of emeralds. Only accidentally the Muzo mine was rediscovered. It is located about 100 miles northeast of Bogota, the capital of Colombia. Nowadays, the Muzo mine is considered the best efficient deposit for biggest emeralds. While most deposits are attributed to volcanic activity or have metamorphic character, the Colombian deposits belong to an entirely different kind in geochemical terms. The Muzo emeralds lay in the black clay slate, an environment rich in organic matter, originating from the Lower Cretaceous period, 120 million years ago.

Exploitation of metamorphic bedrocks, in which the densely emeralds lay, is realized almost everywhere by terrace method. Compact masses of rock have to be moved with extreme caution so as not to miss or destroy the clusters. Only in the Russian Ural mines the deposits are exploited in adit mines. Also significant are the metamorphic emeralds deposits in Leydsdorp in Transvaal, Sandawe in Zimbabwe, Zambia Kafubu Feld, Mingora in Pakistan, Itabira and Santa Terezinha in Brazil, Panczsziru valley in Afghanistan, Maji Moto by Manyara lake in Tanzania, Madagascar Mananjary and others. Also Austrian Habachtalu occasionally mine emeralds.