FORMATION of EMERALDS
There
are two sets of
conditions that can cause crystallization of emeralds. The first is the
interaction
between pegmatitic rock that is rich in quartz and feldspar and basic
or ultra basic rock such as schist and serpentine. The metasomatic
reaction that takes place leads to a sharp rise in temperature, which
takes the two systems to a point where they nearly fuse. Some
particularly active chemical elements wind up exchanged between the two
melts. In the case at hand, elements such as magnesium, chrome and
vanadium, which are mobilized from the basic rock, diffuse in the
acidic system, a process that allows emerald growth. This kind of
crystallization is characterized by a geochemistry regulated by a
metasomatic reaction in a pneumatolitic-hydrotermal (~ 500°C)
environment.
The second set of conditions occurs in area of
complex tectonic structures such as folds, faults and fracture zones.
Interaction between hydrothermal fluids circulating in the
fracture system and surrounding rocks can lead to the formation of
emeralds. Gem quality crystals can be found
in quartz-rich veins that fill
folds in the fracture
system. Many different kinds of rocks can
undergo interaction with circulating
acidic fluids giving rise to a group of characteristics necessary for
emerald precipitation. As in the
preceding case, the reaction that gives rise to emerald is always of
the metasomatic type.