There is nothing more beautiful than a fine quality tanzanite that displays premium rich color with strong trichroic property (blue, purple and red to pink colors are observed). This antique square cushion cut tanzanite is one of these fine quality specimens. The stone measures 8.20 mm, weighs 3.20 carats and has rich bluish purple color with some color-shift under varied lighting conditions. Excellent, near loupe clean clarity and a superb cushion cut deliver top of the line brilliance with bright purple, blue and pink sparks noted within the stone. Prong set the tanzanite is located below a large bail that has three channel set 2.70 mm round brilliant cut diamonds for 0.25 carats total weight. The diamonds are SI2 clarity and H color. The pendant measures 22.50 mm or is a bit less than 1" in length and weighs approximately 4.2 grams of 14K white gold. The bail has two loops for added stability when worn and offers large openings to accommodate a variety of chains. This magnificent piece is offered by Jill Underhill of Color Symphony (http://www.colorsymphony.com) and will be shipped directly from their location in New Hampshire.
This gemstone (or gemstone that is part of this piece of gemstone jewelry) has been enhanced by traditional heat treatment. Traditional heat treatment is used to improve a stones color, remove color zoning/banding, and improve clarity. This treatment is considered permanent. The only way to tell if a colored stone has been treated is for the stone to be analyzed by a lab. Generally only gemstone laboratories have the equipment necessary to make a qualified judgement with any certainty.
Untreated gemstones are rare and should be verified by a lab independent of the seller. A good rule of thumb is to always assume a gemstone has been enhanced, unless valid certification from a reputable laboratory is available. No one that sells jewelry or gems should be doing appraisals, certifications, or analysis. It should always be an independent third party with no vested interest in the sale.