Amber is a very soft material, scoring a maximum of a 3 on Mohs scale of hardness (some samples are as soft as a 1), so be especially careful with metal pliers when wrapping amber in wire. Burmese amber is among the hardest of ambers at a 3, Baltic is in the middle, and Dominican amber can be as low as 1 on Mohs scale. That's because Dominican amber is the youngest - at 20 - 40 million years old!
The gem we call Amber is fossilized tree resin, often mistakenly called fossilized tree sap. The basic difference between these two organic materials is that sap is rather thin, composed of mostly water, and runs deeper in a tree, carrying all of the nutrients the tree needs to live. In contrast, thicker resin runs just under the bark of a tree, and acts as a healing agent should the tree become damaged, blocking any holes or scrapes to prevent fungal disease and/or bugs from entering the tree. Amber is one of few, true organic materials that classify as a gemstone: the others are pearls, certain shells like abalone, jet, ivory, and coral.
The earliest amber recorded thus far, is from the Carboniferous (coal-bearing) time period, about 320 Million years ago! This rare form of amber is kept for scientific research (so don't go looking to purchase it). Amber is one of the oldest known materials used to make jewelry. Naturally it is found in a wide variety of colors, ranging from pale yellow to deep cherry red and in rare instances, blue and green! (Note-if you are looking for what is sometimes referred to as "Black Amber," you really want jet, which is a form of coal.)
These earrings contain Baltic Amber (Dale "Cougar" Armstrong)