Prices may be higher for pieces with inclusions of rare insects. Amber is commonly sold by grams, not carats. 1 gram = 5 carats.
Amber is rarely faceted.
Accompanying value information:
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
The highest values go to those pieces with clearly visible insect inclusions, light colors, and clarity. Since the Jurassic Park movie, the most popular inclusions are mosquitos. Inclusions of plant material, while of great interest to scientists, add little to the value of jewelry. (These inclusions are often too small to be recognized easily). Very large amber pieces are extremely rare. Good quality material is seldom used for anything but jewelry.
For more information on amber quality factors, consult our buying guide.