Except
for Moonstone which are mined
from a weathered pegmatite in
Meetiyagoda and in-situ Chrysoberyl
in Pattara no other commercially
viable gem deposit has been
known to exist in Sri Lanka.
The
recent accidental discovery
of Aquamarine were found during
mining for vein quartz (for
industrial silica quartz) in
the Akkerella estate belonging
to Kahawatta Plantations Ltd.
Which is located about 25 KM
south east of Ratnapura.
Fig
1 : shows the distribution of
Vein quartz at Akkarella Estate,
Opanayake.
Previous occurrences of Auqamarine
in Sri Lanka had mostly been
from Ratnapura & Nawalapitiya
& these stones were always
water worn. The recent findings
have generated a geological
interest in relation to the
genesis of gemstones in Sri
Lanka.
This
vein quartz field stretches
about 2 kilometers in length.
The Aquamarine is found in association
with phlogopite mica and schorl
(black tourmaline) is evidence
of the pneumalytic genesis of
this pegmatite. The size of
the crystals vary but samples
of upto 10cm or more have been
found. The color varies from
a pale sky blue to a darker
blue resembling the color of
Santa Maria Aquamarine. Tests
as to the nature of the fluid
inclusions ib the stone asn
research into the details of
the chemistry of the stones
are currently, being carried
out.
A
few samples of Aquamarine had
been investigated for their
gemmological properties. They
are listes below.
Refractive
Indices: 1.577-1.587
Birefringence: 0.007
Specific Gravity: 2.70
Pleochroism: deep blue &
pale blue to colorless
Fluorescence: inert to short
& longwave
Inclusions: finger prints, doubly
refractive crystlas with reflective
haloes, minute crystals, stringers
of particles, needles, and near
parallel reflective dendrites
surrounded by clouds (Elizabeth
P. Quinn, GIA, Geneva)
The
nearby estate of Hunuwala, which
is about 6km north west of Akkarella,
shows evidence of the continuation
of this pegmatite mineralization.
The National Gem and Jewelry
Authority has recently auctioned
off the Hunuwala estate for
gem mining. Larger crystals
of colorless Topaz have been
found there; some even measuring
up to about 10 kilograms. |
With
a history in gem mining that
goes back some 2,500 years,
Sri Lanka has been known through
the centuries as “Rathnadeepa”,
or the “island of gems”.
Stones
mined on the island include
alexandrite, alexandrite cat’s
eye, amethyst, aquamarine, beryl,
chrysoberyl, chrysoberyl cat’s
eye, citrine, garnet (almandine,
hessonite,
pyrope, rhodolite, and spessartite),
moonstone, ruby, star ruby,
sapphire (blue, golden, orange,
papardscha, pink, white, and
yellow), star sapphire, spinel,
tourmaline, topaz, and zircon.
In modern Sri Lanka, gemstones
are a national resource that
belong to the state. Mining
is controlled by the National
Gem and Jewellery Authority
(NGJA), which has in place an
intricate mining license system
that makes it possible to mine
on private as well as on public
land, with the latter being
managed mostly through a tender
system.
Seeing
that Sri Lanka’s gemstone
exports approach $25 million
a year, it is surprising that
the vast majority of its mines
are small, very labor intensive
operations that use minimal
mechanization. This, the NGJA
argues, is not necessarily a
negative thing, since the gem
mining sector creates employment
opportunities for several hundred
thousand people, including in
support industries such as timber,
water pumps, washing baskets
and other tools, and transportation,
etc. Furthermore, the government
has not encouraged large-scale
mining in order to minimize
damage to the environment. With
these policies in place, NGJA
expects that the known mining
reserves will last for another
100 years.
Ratnapura
is the center of the sapphire
mining industry, with at any
one time between 30 and 50 licensed
pit mining operations active
in the area. Each operation
typically involves five to 50
miners. Heat treatments are
mostly done in Ratnapura and
Colombo. Reportedly, around
700 to 1,000 modern furnaces
are now in operation on the
island.
Aquamarine
in Sri Lanka was usually found
in Ratnapura and Nawalapitiya,
and the stones were always waterworn.
However, a recent accidental
discovery of aquamarine crystals
led to a sudden gem rush. These
stones were found during mining
for vein quartz (silica quartz)
in the Akkerella estate, about
25 kilometers southeast of Ratnapura,
which belongs to Kahawatta Plantation
Ltd. This aquamarine is found
in association with phlogopite
mica and schorl (black tourmaline).
The size of the aquamarine crystals
varies up to 10 centimeters
or more.
The color varies from light
sky blue to darker blue resembling
the color of Santa Maria aquamarine.
Research is now underway into
the fluid inclusions and details
of the chemistry of these aquamarines.
A continuation of the pegmatite
mineralization is found at the
nearby Hunuwala estate, northwest
of Akkerella. The NGJA recently
auctioned the rights to gem
mining at Hunuwala, which has
produced larger crystals of
colorless topaz, some even up
to about 10 kilograms.
Moonstone
comes from the famous moonstone
mines in Meetiyagoda, in the
south of the island, near Galle.
There, the devastation caused
by the December 2004 tsunami
is still very visible, but the
moonstone mines are location
a few kilometers inland and
did not suffer. The production
here, which began more than
50 years ago, is currently very
low. Only two mines are active.
The large high-quality material
with strong blue color and shine
is now a memory only, as the
layers producing these stones
have been depleted.
Currently,
a deeper layer producing smaller
moonstones with a more silvery
hue is being mined. Moonstone
is also being mined near Dumbara,
close to Kandy. This mine has
been producing for more than
100 years and has yielded some
very fine-quality gems. The
best stones ever roduced in
Sri Lanka reportedly came from
this area.
Chrysoberyl
is supposedly mined in Pattara,
but no other commercially
viable deposit of this gem has
yet been found in Sri Lanka.
In the Elahera area, some mechanized
mining is reported, but in general,
openpit mining remains the rule.
During
seasons when agricultural activities
do not require all the local
labor force, 200 to a few thousand
locals dig for stones in their
backyards, which are mostly
rice paddy fields, or in the
surrounding jungle. In Elahera,
unlike in Ratnapura, many women
are involved in mining. The
quantity of gemstones produced
there, despite the number of
miners involved, does not appear
to be high.
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