The name refers to the palish blue, light blue-green or even light green variety of beryl. The green of aquamarine is a watery green without any trace of yellow and is due to iron, not chromium, as can be seen from examination with a gemological spectroscope.
Appearance The most valuable color is a rich, sky blue; but because the stone is pleochroic, even the blue stones have a green or greenish-blue tinge in one direction. Quite large stones, ranging from severalcarats to more than ten or a few tens of carats, are‘ relatively common. Many are virtually free of inclusions. (Again, where there is plenty of material available, poor quality specimensdo hot usually come to market.) The luster is vitreous and not exceptional. The most common cut is the emerald type, although mixed oval or pear-shaped cuts are not infrequent.
Distinctive features The color of this stone, combined with its particular type of pleochroism and vitreous luster, distinguishes it fairly easily from blue topaz and light-blue synthetic spinel, the first being a definite blue color, the second having a gray or violet tinge, much stronger luster and no pleochroism.
Occurrence Most aquamarine comes from the pegmatites of Brazil, where crystals weighing several kilos have been found. Other deposits are in the Soviet Union (Transbaikalia, Urals, and Siberia), Madagascar, the Untied States, and, recently, Afghanistan.
Value Rich blue stones several carats in weight are among the most valuable of secondary gems. They are worth a lot more, for instance, than blue topaz of similar characteristics. Pale or green stones are much less valuable.
Simulants and synthetics Aquamarine is imitated by blue glass, which faithfully reproduces the color, if not the pleochroism, but it is most often imitated by blue synthetic spinel, of a slightly different color, with superior luster and no pleochroism. Because of the general similarity, this is sometimes called synthetic aquamarine, although the latter, as such, is not produced. Light green or yellow-green beryl can be turned blue by heating it to a certain temperature for a certain length of time. This practice has been in use for several decades and is considered acceptable, as with zircon and sapphire.