alexandrite
The mineral or gemstone chrysoberyl, not to be confused with beryl, is an aluminate of beryllium with the formula BeAl2O4. more...
 Home
A
 abercrombie
abercrombie 4
abercrombie skirt
aboriginal
abstract paintings
acceleracers
accordion
acer laptop
acoustic electric
action figure
acura tsx
adriana lima
advantage
advertising
aeropostale
aerosmith
affiliates
afghanistan
agp video
air force
air jordan
air max
air rifle
airtronics
akademiks
alex rodriguez
alexandrite
alice in
alienware
all in
alligator
alltel cell
alpinestar
altimeter
amazon.com
ambulance
american eagle
american flyer
american girl
americana
amplifier
amplifiers
animation
ann taylor
announcements
anthropologie
antik jeans
antique diamond
antique jewelry
antique oil
antique picture
antique sampler
antique violin
apartment
apocalypse
apple ipod
apple laptop
appliance
aqua master
aquamarine
arcade games
architectural
aretha franklin
argentina
armani shirt
arrowheads
art deco
art nouveau
as is
astronaut
at t
atari games
auctions for
audi cabriolet
aurora model
aurora slot
australia
australian gold
autococker
autograph
autographed
autographed baseball
autographs
automatic
automobile
autoradio
avon cape
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
The name chrysoberyl is derived from the Greek words chrysos and beryllos, meaning \"golden\" and \"gem crystal\". Despite the similarity of their names, chrysoberyl and beryl are two completely different gemstones. Chrysoberyl is the third hardest naturally occurring gemstone and lies between corundum and topaz on the hardness scale. Chrysoberyl is a mineral consisting of ordinary colorless or yellow transparent chrysoberyl, cymophane (chrysoberyl cat's eye), and alexandrite.
An interesting feature of uncut crystals of chyrsoberyl are the cyclic twins called trillings. These twinned crystals have a hexagonal appearance, but are the result of a triplet of twins with each \"twin\" taking up 120 degrees of the cyclic trilling.
There are three main varieties of chrysoberyl; ordinary yellow chrysoberyl, cat's eye or cymophane, and alexandrite. Although yellow chrysoberyl was referred to as chrysolite during the Victorian and Edwardian eras, that name is no longer used in the gemological nomenclature.
Ordinary chrysoberyl is a yellowish-green, transparent to translucent chrysoberyl and has often been referred to in the literature as chrysolite due to the common olive color of many of its gems, but that name is no longer used in the gemological nomenclature. When the mineral exhibits good pale green to yellow color and is transparent, then it is used as a gemstone.
Alexandrite, a strongly pleochroic (trichroic) gem, will exhibit emerald green, red and orange-yellow colors and tend to change color in artificial light compared to daylight. The color change from red to green is due to strong absorption of light in the yellow and blue portions of the spectrum. Typically, alexandrite has an emerald green color in daylight but exhibit a raspberry red color in incandescent light.
Cymophane is popularly known as cat's eye. This variety exhibits pleasing chatoyant or opalescence that reminds one of an eye of a cat. When cut to produce a cabochon, the mineral forms a light-green specimen with a silky band of light extending across the surface of the stone.
Occurrence
Chrysoberyl was formed as a result of pegmatitic processes that occurred at least 250 million years ago. High temperatures and pressures from the outer layers of the earth's mantle forced molten magma towards the surface. As the main magma body cooled, water originally present in low concentrations became more concentrated in the molten rock because it could not be incorporated into the crystallization of the localized minerals. Consequently, the remaining portion of the molten magma was water rich. It was also rich in rare elements and silica that still had not solidified. When this water-rich magma was expelled in the final stages of the crystallization, it solidified in cracks and crevasses to form a pegmatite.
Read more at Wikipedia.org
|
