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For centuries, scientists all over the world have
searched for clues relative to the nature of the processes
and conditions that are necessary for the development
of minerals, including gems. Some important answers came
with the discovery of methods for synthesising gemmiferous
materials in the laboratory. From these aimed experiments,
scientists were able to determine the three factors necessary
for the formulation of gemmiferous material: chemical
elements, temperature, pressure.
The type of gem that is able to form in a given location
is determined by the primary materials present in that
environment. For example, quartz, whose chemical formula
is SiO2, can only form where the elements silica and
oxygen are present. And since these elements constitute
over 74% of the weight of the Earth’s crust, it
is not surprising that there is an abundance of quartz
at any given place on the planet. It is, however, rare
to find gem-quality quartz.
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Cristals, structures |
Even if the necessary chemical elements are present
in the environment, relative temperature and pressure
conditions must be correctly balanced in order for a
particular gem to form. If this is not the case, a somewhat
different product will develop. As an example, let’s
look at the behaviour of carbon. Under certain temperature
and pressure conditions, carbon burns and produces a
gas called monoxide, or carbon dioxide. Under other conditions
of temperature and pressure, carbon crystallises into
the material known as graphite. Only under circumstances
where there is a rare combination of extreme heat and
high pressure does carbon crystallise into diamonds.
Our gem has formed! Now what does it take for it to
grow? The growth process of crystals is similar to the
attraction between a magnet and iron objects. Due to
their electrical charges, the atoms of certain elements
are attracted to each other. Once these atoms amass,
they attract other atoms in the environment that then
deposit themselves layer after layer on the growing crystal,
imitating the order of the first atoms from which the
crystal originated and forming the crystal structure.
A crystal continues its growth as long as it is able
to attract new atoms from the surrounding environment
without encountering any obstacles that hinder its development.
This happens rarely in nature. In most cases, environmental
conditions change before a gem-producing crystal has
time to finish growing completely. Even when conditions
remain stable, the neighbouring environment or competition
with another crystal could mean that the growing crystal
does not have sufficient space to reach its completion. |
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