The Guinness Emerald

The Guinness Emerald Crystal discovered in the Coscuez emerald mines is one of the largest gem-quality emerald crystals in the world and is the largest emerald crystal in the collection of emeralds belonging to the Banco Nacionale de la Republica in Bogota, the capital city of Colombia. The origin of the name Guinness is not known, but the elongated, 1759-carat, bright green crystal undoubtedly had all the credentials to enter the Guinness book of world records as the largest gem-quality emerald in the world at least for some years until it was surpassed by other larger natural emerald crystals.


Characteristics of the gemstone


The 1759-carat “Guinness Emerald Crystal” was at one time the largest natural emerald crystal in the world, and is still preserved in its natural crystalline state, at the Banco Nacionale de la Republica in Bogotá. Emeralds crystallize in the hexagonal crystal system resulting in elongated or flattened hexagonal prisms with pinacoidal terminations. But, the “Guinness Emerald Crystal” is an exception, as it is dihexagonal or twelve-sided, also known as dodecahedral. The exact dimensions of the crystal are not known, but the crystal is undoubtedly elongated, with its length between 2 to 2½ times greater than its diameter. The color of the emerald is a bright green color with a slightly yellowish undertone, characteristic of emeralds from the Coscuez emerald mines. The diaphaneity of the emerald is translucent, and some cracks and fissures are visible at the lower end of the crystal. Emeralds from Coscuez are generally more included than those of Muzo and Chivor mines.


Crystal characteristics of Coscuez emeralds


Certain characteristic features of the crystals and the matrix in which they occur can be used to identify the source of the emeralds from the three main mines of Colombia, the Muzo, Coscuez and Chivor mines.


The most characteristic feature of the Coscuez emerald crystals is their frequent occurrence in aggregate type of formations with multiple terminations. The aggregates have a step-like appearance and sometimes a tabular appearance. It is not known whether the “Guinness Emerald Crystal” of Coscuez origin, is also a constituent part of a larger aggregate of crystals. The emerald crystals from Muzo and Chivor do not form clusters or aggregates, however the Muzo emeralds tend to be shorter, while the Chivor emerald crystals are much longer in length.


Color differences and inclusions in the emeralds from the three sources


Muzo emerald crystals tend to have a more saturated color than either Coscuez or Chivor emeralds. Muzo emeralds have a deep herbal-green color. The Coscuez emeralds are generally yellowish-green in color, whereas the Chivor emeralds have a bluish-green color. The Chivor emeralds have a lighter color than either Coscuez or Muzo emeralds. But, using color alone one may not be able to predict the source of the emeralds correctly.


The Chivor emeralds generally have much less inclusions than either Coscuez or Muzo emeralds. The Coscuez emeralds have diffused gardens and inclusions, but have good color and brightness. The Muzo emeralds also have inclusions but are less apparent due to the deep herbal-green color. Muzo emeralds with less inclusions have good transparency.