| |
|
| Specie:
|
Beryl |
| Chemical
Composition: |
Beryllium
Aluminium Sillicate |
| Chemical
Formula: |
BE3AL2SI6O18
|
| Hardness
(Moh’s Scale): |
7.5-8 |
| Fracture:
|
Conchoidal
vitreous |
| Cleavage:
|
Imperfect
|
| Luster:
|
Vitreous,
in polished surfaces |
| Specific
Gravity: |
2.67-2.71
|
| Crystal
System: |
First order
hexagonal prism, tabular habite, flat well terminated surfaces common,
etching and growth marks |
| Optic
Sign and Character: |
U (-) |
| Pleochroism:
|
Varies according
to body color in intensities from weak to distinct varies according
to body color in intensities from weak to distinct |
| Refractive
Index: |
1.569 –
1.575, Varies with origin and locality |
| Birefringence: |
.06 |
Chemical
Elements
Responsible for Color:
|
Chromium,
Vanadium, Iron |
| Fluorescence:
|
UV (Short
Wave): variable, from inert to very pale reddish pink |
| UV
(Long Wave): |
Variable,
from inert to medium reddish pink to red |
| Absorption
Spectra: |
Typical chromium
with doublet in deep red at about 680-685nm line at 635-640 wide
absorption band in yellow. Varies slightly with origin. |
| Phenomena:
|
Chatoyance:
Rare, “Trapiche Star” fix six ray star (Colombian Emerald)
|
| Thermal
Conductivity: |
Medium Low
|
| Reaction
to Heat: |
May cause
fracturing or breakage |
| Reaction
to Chemicals: |
Resistant
to all acids except hydrofluoric acid |
| Electric
Conductivity: |
Beryls in
general are nonconductors |
| Modes
of Formation: |
Hydrothermal
and in Pegmatites |
| Main
Producers: |
Colombia,
Brazil, Zambia, Pakistan, Afghanistan, Madagascar and Russia |
| Oldest
Source of Emeralds: |
Egypt (Not
presently under production) |
| Cutting
Style: |
The ideal
cut depends on the shape and color distribution of the rough material.
The ideal cutting style used is the rectangular or square step cut
known as “Emerald Cut”. Other cutting styles suit Emeralds.
It is common to find Emeralds in oval shape, pear shape and cabochon.
The cushion shape, marquee and round shape cuts are less common.
|
