As this sticky resin oozed from these ancient pine trees, small insects, feathers, plants and other small objects which were in the path of the flow became entrapped in it. As time progressed, the resin became encased in dirt and other debris to become what is called Copal. Over more time, and through pressure and the process of heat, the copal fossilized to become what we now call amber.
The color of amber is usually honey brown but it does come in an array of slight honey colored variations such as bright yellow all the way through to a fairly deep brown color. Brighter colors such as green, red and blue can also be found within the honey colored substance.
Genuine amber can contain insects, which is one of the ways to definitely identify it. Some common insects found in it are gnats, flies, wasps, ants and bees. Every once in a while, one may find more exotic insects encased in the amber such as grasshoppers, beetles, moths, etc. And of course, twigs, leaves and the like are commonly found. Even scorpions, frogs and lizards have been found on rare occasions. Often, bubbles are found within amber.
I've written a more comprehensive resource article on my main site -Vintage Jewelry Lane. The article gives more information about the history and properties of amber and also details the various ways to test it to determine whether your piece of jewelry is genuine amber, or just plastic made to look like it. You can read the full article about amber jewelry here.
The picutre of baltic amber is courtesy of crystal-cure.com