Amber

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Amber
Chemical composition C-H-O compound (fossil resin)
Crystal system Amorphous
Fracture Conchoidal, brittle
Hardness 2-2.5
Refractive index 1.54
Specific gravity 1.05-1.09
Lustre Resinous

Amber.jpg
Amber is the fossil resin from a pine tree that flourished in the Baltic region some 25 to 40 million years ago. Globs of this aromatic sap poured down from prehistoric trees, often trapping insects, twigs, bark and leaves. Amber is one of the few gemstones of organic origin. In ancient India and Egypt, amber was burned as an incense, believed to purify the surrounding area. Amber is abundant along the shores of the Baltic Sea where it is mined extensively from Tertiary glauconite sands that are from 40 million to 60 million years old. It is also from the Dominican Republic.

Reconstructed amber

One type of amber that one may encounter is reconstructed amber. This type of amber is also marketed as "ambroid".
Clear fragments of amber are carefully selected and heated upto ± 180° C under high pressure of 5000 psi + (34473785 Pa) in a reducing atmosphere with sometime linseed added. Under these conditions the fragments fuse together and some organic dyes may be added to the process to influence the color of the resulting solid block.

Characteristics

The following inclusions may be seen:

  • flow lines
  • elongated bubbles

A strong bright blue fluorescence might be observed.

Treatments

Heat treatment

Alot of amber contains many gas bubbles that give it a hazy appearence. Slow heating between 150-180° C, followed by slow cooling, can diffuse these bubbles out.
When the cooling takes place too rapidly, typical leaf like stress inclusions form (these are know as "sun spangles") and these inclusions are, more than often intentionally, mistaken for prehistoric leaf inclusions.

Another type of heating involves laying the specimens in a sand filled iron pot and heat it over an extensive period to darken the amber. This gives it an "antiqued" look. Natural amber may darken naturally over time due to air oxidation.

Other treatments

  • Dying
  • Coating
  • Foiling

Sources

  • Gemstone Enhancement (1984) - Kurt Nassau ISBN 0408014474