Lighting
The proper lighting conditions for
tourmaline will depend on the color variety. Reds, oranges
and yellows generally look best under incandescent light,
while greens, blues and violets appear prettier under
daylight. When buying any gem, it is always a good idea
to examine it under a variety of light sources, to eliminate
future surprises.
Clarity
Different varieties of tourmaline tend
to have different clarities. Thus while large clean
tourmalines in the blue and blue-green colors are available,
almost all red and pink tourmalines will show eye-visible
inclusions. The most common inclusions in tourmaline
are fractures and liquid-filled healed fractures. Needle
inclusions are also common.
Shape
& Cut
Faceted tourmalines (those with flat
polished faces) are found in a variety of shapes and
styles. Due to the prevalent long acicular crystal shapes
of tourmaline, emerald cuts and fairly elongated emerald
cuts are commonly seen. Ovals and cushion cuts are common,
as well as other shapes such as emerald cuts and hearts
shapes.
A perfectly cut tourmaline should always
exhibit good symmetry and polish conditions, facets
should be aligned straight in relation to the gem’s
girdle, and also to each other. Polish conditions should
be good with no visible surface pits or polishing lines.
Cabochon cuts are most commonly applied
to those tourmalines whose clarity is not ideal for
faceting. However, they are also used to develop and
display cat’s eyes in chatoyant tourmaline. Well-cut
and proportioned cabochons with good symmetry, which
are semi-transparent with smooth un-cracked domes, are
the ideal.
Stone
Sizes
Paraíba tourmalines are extremely
rare in faceted stones above 2 cts. Fine Paraíba
above 5 carats can be considered world-class pieces.
Most stones tend to be less than 1 ct. Chrome tourmalines
of quality are rare in sizes above 10 cts., as are rubellites.
Sources
Tourmaline is a pegmatite mineral and
so is mined from the world’s great pegmatite districts.
Foremost is Brazil, but fine tourmalines are also found
in San Diego County, including the famous Pala pegmatite
district, and Maine. The East African countries of Kenya,
Tanzania, Mozambique and Madagascar have also produced
fine tourmaline in the past. Beautiful yellow “canary”
tourmalines come from Malawi, while extremely fine rubellites
and blue-green tourmalines are found in Nigeria. Afghanistan,
Sri Lanka and Burma also produce gem tourmalines on
occasion.
Carat
Weight
Tourmaline frequently occurs in large
crystal sizes and such large specimens can be thought
of as being fairly accessible. Large crystal sizes also
help to enhance tourmaline's perceived depth and richness
of color.
Similar to most other gems, when the
carat weight of a tourmaline increases, so does the
price per carat. However, large tourmaline crystals
with their abundant occurrence rates are simply more
plentiful than in habitually smaller gems such as ruby
and sapphire. This means that weight related price jumps
in tourmaline are less severe than in ruby and sapphire.
Indeed, it is not uncommon for comparable quality 3
Carat, 4 Carat, and 6 Carat tourmalines all to have
the same or very similar per carat prices – something
that is unthinkable regarding diamond, ruby and sapphire.
The Use
Of Heat
Many tourmalines seen on the market
today have been subjected to high temperatures in an
age-old practice that is said to have originated in
Sri Lanka some 2,000 years ago. They are heated at high
temperatures to improve their clarity and to intensify
their colors. However, there are also many tourmalines
on the market are not heated. Unusually, the market
makes little or no distinction at all between the heated
and non-heated specimens.
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Tourmaline,
a perennial favorite of the gem world has long been
one of the most consistently popular gem types available.
Although not as glamorous as ruby, sapphire or emerald,
in reality the beauty of tourmaline and the value of
certain tourmaline types means they can be as every
bit as precious.