As early as the Middle Ages, colorless beryls were beaten and polished in such a way that they could serve as “magnifying glasses”. In a time when paper was scarce and letters were closely written, this was necessary.
Emerald means “green stone”, it is colored green by a trace element: Chromium. This is present at the same time and place rare in the genesis of beryl, correspondingly rare are emeralds worldwide.
The interesting thing is that emeralds occur in shales or calcite veins. The deposits are steadily dwindling, even from the main supplier country Brazil the raw material is scarce and prices are rising. Emerald deposits in Ethiopia have not recently been found to contain as many emeralds after professional mining operations began as small-scale mining did years earlier.