Indian Jeweller (IJ) Magazine August -September 2019

Spinel
Spinel is irresistible: it comes in many
colours including a rare vivid red colour
that rivals ruby. In fact, many of the
famous “rubies” of history are actually
spinel. Burmese lore says spinel crystals
were “polished by the spirits” because
they are often such a beautiful shape.
It is known to be a symbol of power,
victory and new hope.
Colour
Spinel comes in a range
of hues – orange, intense
red, pastel to vibrant pink, all
shades of purple, blue and violet
through bluish green. Traces
of chromium cause intense red
and pink colours. Orange
and purple are caused by
a mixture of chromium
and iron. The presence of
iron creates violet to blue
spinel, but if cobalt is present
too, it can produce a rare,
saturated blue colour.
Clarity
Lighter colours of spinel are usually relatively free
of inclusions. Saturated reds and blues are rare and
sometimes included. Some spinel has interesting
inclusions that reflect the gem’s octahedral crystal
growth. Groups of these microscopic inclusions can
resemble human fingerprints.
Treatments
Some spinel may be heat treated to improve clarity, but
it is a stable treatment. In rare cases, spinel may also be
fracture filled to improve its apparent clarity.
Sources
Fine large red spinel crystals, historically referred to
as “Balas rubies,” were mined in central and southeast
Asia. Key mining locations are Myanmar (formerly
known as Burma), Tajikistan, Sri Lanka, Vietnam,
Tanzania and Madagascar.
To learn more about spinel and other popular gemstones
visit GIA.edu/gem-encyclopedia
This article is provided by GIA (Gemological Institute of America ® ).
GIA.edu
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