'Amber' is a fossilized form of

The correct answer is Hardened resinous secretion.

Explanation:

• 'Amber' is a fossilized form of hardened resinous secretion.
• Resin is a sticky, viscous substance secreted by plants to protect them from predators and pests.
• Amber is made from resin exuded from tree bark, but it can also be found in the heartwood.
• Resin protects trees by filling gaps in the tree bark.
• When resin covers a break that is caused by a chewing insect, it hardens and forms a seal.
• Thus amber often contains insects preserved in it as they might have got stuck in the sticky resin years ago.

Important Points

• Colour - All shades of yellow.
• Shape - Irregular nodules, rods or drop-like shapes.
• Occurences - Largest deposits are found along the shores of Baltic Sea.
• Some other properties:
  • It may contain microscopic air bubbles.
  • Baltic amber often contain minute hair-like inclusions, apart from insects.
  • The surface changes its colour and opacity on exposure to oxygen in air - it becomes darker and opaque.
  • When kept in oxygen-free environment, they retain their original colour and appearance.
• Uses -
  • Deeply coloured translucent or transparent forms are valued as gems.
  • Used for making decorative items and jewelry.
  • Healing agent in folk medicine.
  • Study of fossils that are preserved inside the hardened resin.
  • It is also used for aesthetic purposes.
  • In ancient times, it was used as a natural magnifier.
  • Transparent amber with a convex surface was used as burning lenses for concentrating sun's rays.