Besides the Oriental emerald, which, as previously mentioned, is a form of corundum, there is the ordinary emerald found in Peru, Columbia, Bolivia and Siberia. This is a variety of beryl, from which, however, it is distinguished by its colour of emerald green instead of pale green, light blue, yellow or white, the colours of the beryl. This shade of green is produced by the presence of chromium, those of the beryl arising princi¬pally from the presence of iron. The precious emerald is valued, in commerce, next to the ruby and diamond, sometimes before the latter.

The search for emeralds requires great patience and industry, for disappointment is more frequent than success. Often there is little or nothing to guide the prospector, the whole formation of black carbonaceous limestone being covered with earth to a depth of from six to thirty feet, as at Muzo and Cosquez in Columbia, where some beautiful gems are found embedded in. veins of calcite, the veins sometimes being less than six inches in depth.

The earth deposit, frequently covered with jungle, has to be removed before prospecting is possible, and a break may prove quite valueless after months of work have been expended upon it. Emeralds which are exposed in the course of quarry¬ing are carefully loosened and detached from the matrix by a ” pricker,” the other quarried material being broken up by light hammers in sorting sheds. The fragments of these remains are closely examined for gems. Some of the stones found thus can be picked out clean. Others have to be cleansed from the adhering matrix, by treatment with cold dilute hydro¬chloric acid.

Before being marketed, the emeralds are sorted into about fifteen different grades.
Emeralds have been found in different parts of the Andes since the sixteenth century, and the deposits around the district of Muzo, Columbia, previously mentioned, are believed to be inexhaustible, in spite of many disappointments.