| The
chrysoberyl family is best known
for the more valuable alexandrite
and cat's eye varieties. The optical
properties of chrysoberyl cat's
eyes make these stones the most
famous and popular of all cat's
eye type stones.
|
| Gemological
Information |
| Color
: |
Yellow,
Greenish Yellow, Yellowish Green |
| Refractive
Index: |
1.741
- 1.760 |
| Chemical
Composition: |
BeAl2O4 |
| Hardness: |
8.50 |
| Density: |
3.73 |
| Crystal
Group: |
Orthorhombic |
| Ocurrence: |
Sri
Lanka (Ceylon), Tanzania, Russia,
Madagascar, Brazil. |
| Cat's
eye chrysoberyl is also known as
cymophane, - then name being derived
from the Greek words cyma and phanes,
meaning “wave” and “appearance.”
Microscopic needle-like inclusions
inside the stone reflect a streak
of light known as the cat’s
eye. The cat's eye’s inclusions
are aligned parallel to the crystallographic
axis and they are always cut as
cabochons with the fibrous need-like
inclusions running across the narrow
part of the stone as this is the
only way to display the effect properly.
The effect becomes most apparent
under a spotlight or under direct
sunlight. A thin bright band of
light will appear and open and close
as the stone is rotated –
hence the eye like effect. This
phenomenon is also known as chatoyancy,
which comes from the French chat
for cat, and oeil for eye. |
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