Jewelry Lovers

Twenty-four goldsmiths worked continuously for six years to make the finely chiselled and richly ornamented Crown of the Andes from one massive gold nugget. This splendid jewel is adorned with 453 emeralds of a total weight of 1,521 carats. Today, each carat attains a valuation price of $3,000. After a long odyssey this treasure, estimated to be the most valuable in the world, landed in the United States a few years ago. These gems scarcely ever came directly from their source; for neither torture nor fear of death was able to prize from the Inca priests the secret of their emerald localities. On the contrary, in their boundless thirst for revenge, they obliterated every trace. The work of destruction was carried out so completely that in the end it was by chance that the Muzo mine—the most productive hoard of today’s most splendid emeralds—was rediscovered, and only at the beginning of the present century was the Chivor mine near the village of Somondoco found. The other emerald deposits known today in Colombia have been gradually made accessible.

The allure and aura of this mysterious green precious stone are further magnified when one realizes that in millions of years a chance concatenation of circumstances must have occurred in the earth’s interior in order to have given birth to this gem. The overwhelming majority of emerald occurrences belong to the pegmatitic phase, although in fact the most important deposit at Muzo can hardly be credited to it entirely; it seems rather to fall in a transition stage between the pegmatitic and hydrothermal phases. The growth cavities of the emeralds are here located in unmetamorphosed sedimentary calcareous shales, whose age of 1 3o million years reaches back to the Lower Cretaceous Period. Pegmatites are present deep underground and indicate the proximity of the magma. The emerald-bearing veins which traverse the calcareous shales seem to have been formed near the surface and therefore under relatively low pressure; they contain many druses of varying sizes. The emerald crystals have grown inside them from hydrothermal solutions, often very freely, and thus are well developed. Many individual ones are relatively clear. The accessory minerals, apatite, fluorite, and barite, which are profusely present, indicate a hydrothermal content in the solutions.

The emeralds of Chivor, the other major occurrence in Colombia, originate in a hard, metamorphic matrix, which in its composition approaches a pegmatite. It crops out in veins and gangues which often widen out into considerable cavities. The emeralds which have grown in them, mostly unhindered, show well-formed crystals. Unfortunately they are somewhat paler than the deeply colored Muzo crystals because of a lower chromium content. Little is known of the geological conditions of the other Colombian emerald occurrences—Burbar, Cosquez, Gachala, and so on. It appears, however, that they resemble those of Chivor rather than those of Muzo.

All other emerald deposits of the world differ from these rather atypical Colombian occurrences in their connection with chrome-bearing metamorphic schists. The emerald deposits of the Urals—for ninety years the most important after the Colombian ones but today without importance—are situated on the Siberian side of the mountain chain on the Tokowaya River northeast of Sverdlovsk, the former Ekaterinburg, where in the night of 16th/17th July 1918 the Czar and his family were murdered. There, in 1831 after a storm-lashed night, a considerable number of emeralds were found in the roots of a fallen tree. The matrix is a biotite mica schist, which is penetrated by talc and chlorite schists and which has been contact metamorphosed by a nearby granite massif and intrusive pegmatites. The accessory minerals are typical of the pegmatitic-pneumatolytic phase. Those minerals, however, which in Colombia suggest a transition to the hydrothermal phase, are completely lacking. The many large emerald crystals are mostly of poor color and dull. Only the small specimens have good colors.

Conditions are similar in the emerald deposits in South Africa, Rhodesia, and in the Habachtal in the Austrian Alps where pegmatites have intruded extensively into mica schists. The pegmatites brought beryllia and alumina as well as silica, while the chromium originated in the mostly greenish mica schists. Significantly the deep green specimens are found predominantly in the mica schists. The emeralds of South Africa and from the Habachtal are very similar to those of the Urals, while the Sandawana emeralds from Rhodesia excel in their fresh, lively green, which very soon after their discovery in the year 1956 brought them into favor with the connoisseur.

Emerald is one of the few gemstones which is mined from its matrix, in other words, from primary deposits. At most emerald mines the exploitation methods are still extremely primitive. The unusual mode of occurrence does not allow a simple cleaning out of the irregularly spaced gangues and cavities, but rather the whole solid rock must be mined so as not to risk overlooking possible rich pockets by a few centimeters. Nearly all mines are therefore exploited by open cast methods. Over a whole mountainside or round a whole hill steps or terraces are cut. The miners stand in a row with their backs to the hill slope and plunge 3-meter long crowbars, weighing 15 kg., into the relatively crumbly rock. The front end of the bar is pointed to enable better penetration into the ground, and the other is wedge shaped and tapering, to break up the rock. In the Cobra/Somerset occurrence near Gravelotte in the Transvaal (South Africa) massive pegmatite cones have pushed up into mica schists and have led to emerald formation. Here the most modern mining methods and installations are used.

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