|
|
|
|
Synthetic
Spinel
The first synthetic spinel was produced accidentally
when some magnesium oxide was added to the feed powder
in making synthetic Ver¬neuil corundum. Spinel was
not considered an especially valuable gem, however,
so more than 20 years passed before synthetic spinel
was used commercially in quantity.
|
|
Natural
spinels are not commonly encountered in the gem trade,
but synthetic spinels are seen almost everywhere. |
| |
|
These
gems are widely used to imitate other gems that are considered
more desirable, such as emerald, aquamarine, and tourmaline.
Synthe¬tic spinel is normally made by the Verneuil process,
and boules in a tremendous variety of rich colors can be grown.
|
|
 |
 |
|
Synthetic
Spinel |
| Synthetic
Spinel
These
colors are due to the addition of chemical impurities
because pure spine], as with pure sapphire, is
colorless. In addition, spinel powder mixed with
cobalt oxide and fused in an electric furnace
produces a dense, deep-blue material that strongly
resembles lapis lazuli.
A spinel
that resembles moonstone was introduced in 1957.
Some spinel has also been made by flux fusion,
but this material has not been used much as gems.Synthetic
spinels may not show the curved growth lines seen
in synthetic Verneuil corundum.
.
|
|
|
 |
But
they can be identified as spinel, and the colors of the synthetic
gems are usually sufficiently different from those of natural
spinels to make identification possible
|
 |
|
|
|
