|
|
Kauri Gum, Kauri Copal, Kauri Gold...
|
Northland Green Gecko (Moko)
Naultinus grayii |
|
Kauri Gum is the fossilised resin or sap
of the Kauri Tree. These enormous trees produce vast
amounts of sap which congeal into lumps when the tree
is injured. The sap hardens into a resin and becomes a
form of Copal. Kauri Gum comes in many shades and colours, from
almost completely clear up to almost black. Dark Red and
Green pieces are occasionally located.
Kauri gum will eventually harden to a point where it
is fully fossilised and is more accurately described as
Amber. Some Kauri Gum found in the Otago
in the South Island has been estimated by scientists to
be over 175 million years old.
Most of the Kauri Gum found on the
Gumdiggers Park site is around 100,000 years old. |
|
 |
|
The debate over the classification of Kauri Gum has gone
on for many years. Kauri Gum is sometimes known as New Zealand
Amber. However there is disagreement amongst geologists and no absolute
rule applies although the New Zealand Rock Hound Society is trying to
establish a firm classification.
However, in general, young gum that is not fossilised is known as Kauri Gum. It is readily melted and is not able to be
polished to a high shine. Often it is "milky" or "cloudy"
and a thumb nail can be pressed into the gum, leaving a mark on the
surface. The
outside surface also "crazes" (develops fine cracks) quickly so is not really suitable for
making quality Jewellery. In earlier times it was often melted and had
"inclusions" placed inside and passed off as Amber. |
 |
|
Kauri Gum which has aged to the stage of
being sub-fossilised is properly known as Kauri Copal, Copal being derived from
the Spanish word “copalli” meaning incense. Other types of copal are
usually used for this purpose (frankincense is probably the most well known) but Kauri Copal
has a distinctive and
pleasant smell.
It is more durable that Kauri Gum and is easier to polish and
the shine will last on the surface for longer. Kauri Copal is often
referred to as a "sub-fossilised resin". It can be many hundreds
of thousands of years old. |
 |
|
Most of the pieces seen today fall into this "Copal"
category. Unfortunately there is a huge variation in the characteristics
of individual pieces of the Kauri Copal. Only the older, harder forms
are really suitable for making into jewellery or carving.
It is almost impossible to determine this by
non-destructive methods. There are other tests available but they
involve the use of scientific measuring equipment not normally
accessible to most people. |
 |
|
"New Zealand Amber" is older and harder again than Kauri
Copal and is fairly rare. Some of it is millions of years old and passes
all the test for Amber. It has
undergone the process of polymerisation where the chemical structure has
changed and the gum is fully fossilised.
It polishes to a high shine and is a
true gemstone. A common test for Copal versus amber is to place a
small drop of ether on the surface (or other form of alcohol, nail
polish remover will do). Amber will not be affected whilst
Copal will turn sticky. Another test needs only an open flame; Copal melts when placed next to a hot
flame whereas Amber will become discoloured and turn sticky but stay
intact.
|
 |
|
Perhaps whether it is classed as NZ Amber or
Copal is unimportant. Baltic Amber is still being mined today and the mines
are estimated to last another 300 years.
Kauri Gum/Copal/Amber is much rarer, no
new supplies are available and very little remains outside of museums.
It comes in a huge variety of colours and patterns and no two pieces are
the same. Prices for individual pieces and jewellery are rising rapidly.
|
 |
 |
