I asked my mom today how emeralds are formed.
So, we read that:
"Emerald crystals, as with other natural gemstone crystals, grow one molecule at a time. Each molecule is positioned in the crystal matrix under the optimum conditions. Sufficient time and space is required to allow a gem-quality crystal to grow. The natural Emeralds that are being mined today are actually relics of geologic events that took place hundreds of millions of years ago, deep in the Earth’s crust.
Emerald crystals may form in hydrothermal veins if the necessary conditions are present and if the necessary elements (like beryllium) are present. These hydrothermal veins occur when hydrothermal fluids escape from magma deep in the Earth’s crust.
These fluids may contain adequate concentrations of the elements necessary to build a natural Emerald crystal. When they do and if the conditions are optimum, an Emerald crystal may begin to take shape as the hydrothermal fluids begin to cool in deposit veins that have fractures in them. Almost all Emeralds that are sourced from Colombia are formed in this manner. Many of these Colombian Emeralds are associated with calcite deposits that are also formed in the hydrothermal process."
Here's the website we referred to for this information.