Beryl
Be3Al2Si6O18;
Beryllium Aluminum Silicate
Beryllium is another rare and very
hard mineral that forms in several different ways:
1) Some beryl deposits have been found
in rocks of intrusive, igneous origins, such as cavities within granite
and pegmatite. Beautiful red beryl crystals have also been found in
extrusive, volcanic deposits.
2) Other forms of beryl have also been found in metamorphic rocks where
the basic elements that form beryl (beryllium, aluminum, and silicates)
leach out of intruding granite that pass into the adjacent, silica-poor
rock formations where they crystallize.
3) Greisens
are another type of rock in which beryl may be found. Greisens are formed
when extremely hot, mineralized water passes through fractures and cracks
in granitic rock. This superheated mineral water alters the granite
host rock in a process known as hydrothermal alteration.
In its purest natural (uncut) form,
this mineral forms long, hexagonal prisms and is known as goshenite.
It also comes in a variety of colors, depending upon the mineral impurities
that have entered the crystal during its formation. Unlike sapphires,
several different colors of the mineral beryl are separately classified
gemstones. Some of the lesser known variants of the mineral beryl are;
heliodor (yellow), morganite (pink),
aquamarine (pale blue-green), but the best known, most
highly valuable variant of beryl is the deep green emerald...
Emeralds
The element that gives emeralds their
beautiful green color is the same element that turns corundum into red
rubies - chromium. The base mineral composition of rubies differs
from that of emeralds (Al2O3 for rubies, Be3Al2Si6O18 for emeralds)
so the chromium trapped within the crystal lattice of each absorbs different
colors of the visible spectrum of light; the chromium in rubies reflect
red and the chromium in emeralds reflect green.
Unlike other precious gemstones, impurities,
inclusions (gas bubbles and other minerals), small fractures, and other
intrusions into emerald crystals do not detract from the value of a
stone. On the contrary, the minor imperfections found deep in the interior
of a transparent, natural emerald are what give it "character"
and assure the owner that is truly unique, original and unaltered stone.
The largest uncut
emerald was found in Carnaiba, Brazil in 1974. It was
an incredible 86,136-carat natural beryl crystal. The stone was eventually
valued at $1,120,080 USD. The largest emerald crystal ever discovered
was 7,025 carats and was found in a mine in Colombia.
