Emerald is a compound made of Beryllium,
Aluminum, Silicon and Oxygen with the formula,
Be3Al2(SiO3)6. The green color of Emerald is due to traces of Chromium present in them.
It is very interesting how
different minerals and gems exhibit brilliant
colors. Let's first understand why we see color
around us. White light contains rays of all the
colors. When white light is passed through a
prism, one observes the separation of different
colors contained in white light. A substance
appears black because it absorbs all the different
colors shone on it, whereas a blue substance
absorbs everything except blue; what is left after
absorbing is what one sees as color.
Many minerals in their pristine state are
colorless, which means they do not absorb any
color. They appear transparent. But, if some
specific impurities are added to the mineral, the compound assumes an interesting color. The
mechanism as to why a specific impurity produces a
specific color is a question often asked by
scientists, but the answer is complicated in most
cases. But, for most well-known minerals, we know
the reason why.
Emerald like many other gemstones such as ruby,
sapphire owe their color to impurities present
within them. In fact, Ruby and sapphire are
made of exactly the same material (Corundum, which
is a compound made of Aluminum and Oxygen with
stoichiometry Al2O3), but
ruby appears red and sapphire appears blue. The difference in color is due to traces of Chromium present in ruby, whereas blue Sapphire obtains its color from traces of Iron and Titanium impurities.
Emeralds are made from 4 elements that are
found deep in the Earth’s crust: beryllium,
aluminum, silicon, and oxygen. These elements
are found flowing in veins filled with hot water
called hydrothermal veins. When the conditions are
just right in these veins and the cool down, the
emerald crystals start to form. Emeralds can
also be formed in magma rather than hydrothermal
veins. A lot of the emeralds we mine today are
the result of processes that happened hundreds of
millions of years ago.
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