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1 Amber and copal Amber and copal are tree resins, which are materials produced by some
trees as a form of protection. Resin usually runs down the trunk under
the bark and seeps out if the bark is damaged or broken. Resin should
not be confused with sap, which is a nutrient-bearing substance
contained in all plants.
There are many resins that can resemble amber and copal, but these
are the only two that can be termed gem materials.
Put very simply, copal is young version of amber. There is no definite
age at which copal turns into amber, as the process is continuous from
the moment the resin appears on the tree and begins to solidify. In
physical terms, when the resin is sufficiently cross-linked and
polymerised it becomes amber (see Chapter 13). In other words, the
resin has dried out and hardened. This process takes thousands if not
millions of years, and not all copal becomes amber as much of it disin-
tegrates with time. Furthermore, as the process is such a long one it is
not possible for us to follow it or to replicate it in a laboratory, so there
is still much that is speculation. We know, however, that there are some
instances of copal that have begun to look like, and take on, the proper-
ties of amber.
Ambers
Amber deposits are found worldwide and are reckoned to be from 300
to 15 million years old. The two best known deposits are those in the
Baltic region and in the Dominican Republic.
There are few signs of the forests that once produced the original
resin as they are long gone. They have been washed away with the
changing land masses of the planet, and died off as the climate became
colder in the north.
Amber is too old for carbon dating, so one method used for deter-
mining its age is by dating the geological layers in which it is found.
However, this method can be confused by the fact that many amber
deposits are secondary, for example much of the Baltic amber was
1 Amber and copal moved to its present location by melting ice between past Ice Ages.
Burmese amber was long thought to be about 45 million years old, but
recent research suggests that it probably originated elsewhere and not
in its present location. It is therefore a secondary deposit, making it
much older, at between 100 and 80 million years old. This conclusion
was reached by studying the insect inclusions, which did not match the
age of the rock strata in which it lies.
While many gem materials contain inclusions, amber is unique in
that it can contain inclusions of plant and animal matter flora and
fauna. These have become stuck to the sticky surface of the resin as it
oozed from the tree. They may have inadvertently landed on it, or they
may have been blown onto it by the wind. In the case of stingless bees,
it is thought that they gathered the resin for nest building. Other
trapped creatures have included termites, ants, flying ants, butterflies,
moths and damsel flies, or anything too small or weak to be able to
extricate itself.
Plant inclusions are those that were light enough to be blown on the
wind, or picked up on the forest floor at the base of the tree when the
resin reached that far. There have been very rare findings of tiny frogs
or scorpions. As time passed the insect or plant matter became encap-
sulated in the substance which, due to its chemical properties, dried
out the object without shrinking it, sterilised it and finally hermetically
sealed it for us to examine millions of years later. It is because of this
preservation that we are able to learn much of what the world was like
all those years ago, long before man emerged on this planet (Figs
1.11.5).
Baltic amber
Known as the Gold of the North, Baltic amber is the best known of
all ambers. It has the longest history and is the most plentiful.
Around 50 million years ago Scandinavia and the Baltic formed one
land mass covered in forests. The climate was subtropical. It is here that
Baltic amber was formed between 45 and 30 million years ago. It possi-
bly came from different trees, though the one which is popularly thought
to have produced the resin has been named
Pinus succinifera
, as it bore
fruit resembling pine cones and the resin contains succinic acid.
Deposits occur in the eastern Baltic from Poland to Estonia,
especially around the Samland Peninsular. Here it is mined in large
quantities.
Baltic amber is found as secondary deposits in much of Denmark
and southern Sweden, in layers laid down 30 000 years ago. It is not
mined but turns up when foundations are laid for bridges or buildings,
or it is washed up on the beaches after storms that dislodge the mater-
ial from the seabed. Occasionally it also washes up on the north
Norfolk coast of England.
2
GEMS AND ORNAMENTAL MATERIALS OF ORGANIC ORIGIN AMBER AND COPAL
3
Figure 1.1
Insect in Baltic amber, showing typical white coating.
Figure 1.2
Fungus gnat in Baltic amber. 4
GEMS AND ORNAMENTAL MATERIALS OF ORGANIC ORIGIN
Figure 1.3
Flower head in Dominican copal.
Figure 1.4
Damsel fly in Dominican amber. Structure and properties of Baltic amber
Baltic amber is the most varied in colour and transparency, ranging
from creamy opaque through transparent golds to almost black, and
often occurring as a mixture of different shades and transparencies
(Fig. 1.6).
Amber consists basically of carbon, hydrogen and oxygen, with
traces of other elements. Baltic amber contains a much higher
percentage of succinic acid than any other amber and is therefore
sometimes named succinite. (To some purists, only succinite is
real amber. Other ambers, which contain no succinic acid, are then
called retinites.).
Rough amber has a dull, matt appearance and unless broken shows
little of the golden glow of the polished article.
Amber breaks with a conchoidal fracture, revealing transparent
colours ranging from pale yellow, golds, honeys, brandy to almost
black. In opaque colours it ranges from pale cream to mid- or dark-
reddish brown. Usually a single lump will contain a variety of
colours and opacities (Fig. 1.7).
The opaque appearance of some amber is caused by minuscule air
bubbles trapped inside the material the smaller the bubbles the
more opaque and paler the material. One square millimetre of
AMBER AND COPAL
5
Figure 1.5
Poorly preserved bark lice in burmite. 6
GEMS AND ORNAMENTAL MATERIALS OF ORGANIC ORIGIN
Figure 1.6
Pieces of Baltic amber rough and half-polished, showing varia-
tions in colour.
Figure 1.7
Piece of Baltic amber rough, showing different opacities and
conchoidal fracture. opaque amber can contain anything from 600 to 900 000 bubbles
(Fig. 1.8).
Baltic amber is rich in inclusions and over 1000 varieties of flora
and fauna have been discovered embedded in the resin. Unique to
Baltic amber are hairs from oak flowers and tiny crystals of the
mineral pyrite. Other inclusions are flowers, leaves or pieces of bark,
and various insects, the most common being termites and ants.
Most of these things are now extinct, but a few species are very
closely related to insects or plants alive today (Fig. 1.2).
An opaque, white matter is often present around an insect inclu-
sion. This is thought to be a fungus formed by the partial decay of
the insect, and is unique to Baltic amber (Fig. 1.1).
Baltic amber fluoresces pale, chalky yellow to chalky pale blue under
ultraviolet light. The opaque areas fluoresce more than the trans-
parent areas.
AMBER AND COPAL
7
Figure 1.8
Baltic amber beads: heat treated and natural. Dominican Republic
The second most plentiful amber, that from the Dominican Republic,
is younger, at between 25 and 15 million years old. Some of it is
believed to be the resin from a shrub of the genus
Hymenaea
, but
several different types occur, with varying ages and different physical
properties.
This amber is also mined, occurring in veins of lignite in mountain-
ous areas.
Structure and properties of Dominican amber
Dominican amber looks very different from Baltic amber. It is
almost always transparent and of yellow to reddish-brown hues, or
occasionally a pale greenish-yellow. It contains very large quantities
of black substances picked up as it formed (Fig. 1.9).
It is very rich in inclusions that are magnificently preserved, and are
usually clearly visible in the transparent resin (Fig. 1.4).
It contains no succinic acid and is sometimes termed retinite. It can
show strong green, blue or beige fluorescence under ultraviolet light.
The green or blue can also sometimes be seen in daylight.
Mexican
Mexican amber comes from the Chiapas region. After being unobtain-
able for some years, it is again appearing on the market, though in
small quantities only. It is between 30 and 20 million years old and,
8
GEMS AND ORNAMENTAL MATERIALS OF ORGANIC ORIGIN
Figure 1.9
Pieces of rough amber from the Dominican Republic. AMBER AND COPAL
9
Figure 1.10
Polished Mexican amber pieces, showing variations in colour.
Figure 1.11
Polished Mexican amber showing parallel lines of debris. 10
GEMS AND ORNAMENTAL MATERIALS OF ORGANIC ORIGIN
Figure 1.12
Frog carving in Mexican amber.
Figure 1.13
Frog carving showing fluorescence in daylight. like Dominican amber, it originates from a tree of the genus
Hymenaea.
It is much sought after and popular for use as a material from which
to make good-quality carvings.
Structure and properties of Mexic