Light blue, blue, blue-green.
Mohs’ hardness: 7 1/2- 8.
Refractive Index: 1.577-1.583
Countries of Origin: Aquamarine deposits are found on all continents. The most important ones are in Brazil (Minas Gerais, Bahia, Esperito Santo), where the host rocks are pegmatite and coarse-grained grantite. Numerous finds have been made in the inner highlands of the Malagasy Republic.
The well-known deposits in Russia, the Urals and Transbaikalia appear to have been worked out. All other deposits are of only local importance: Australia (New South Wales), Burma, Sri Lanka, India, Kenya, Mozambique, Zambia, South Africa, Namibia, Tanzania and the U.S. (Colorado, Connecticut, California, Maine, North Carolina.)
In History, Literature and Lore:
Aquamarine comes from two Latin words meaning “water” and “sea.” The first documented use of aquamarine is by the Greeks between 480 and 300 B.C. Amulets of aquamarine were thought to render sailors fearless and protect them from adversaries as sea, especially if the stone was engraved with Poseidon on a chariot.
The largest aquamarine of cuttable quality was found in 1910 in Minas Gerais, Brazil. It weighed 243 lb./110.5 kg., and was cut into many stones. There have also been finds weighing several tons, but the aquamarine was gray and opaque, not suitable for jewelry.
What to Look For:
Because of inclusions of foreign substances, the physical properties of aquamarine can vary.The pigment comes from iron.
Typical inclusions are fine hollow rods that can reflect white light. Where growth lines are seen in larger numbers, a catseye effect or six-rayed star might even be possible.
The stone should be clean under a 10-power loupe. At best it should be a bright sky blue, though some people like a little greenishness, which shows that it is an untreated stone, and gives it a rich, antique feeling.
The lesser stones are those which appear watery and colorless. Aquamarines with intense color are becoming very scarce. Lower quality stones-- greenish yellow, greenish and even brownish beryls-- are heated to 752ºF/ 400ºC to change them to the desired aquamarine blue. The color change is permanent.
“Synthetic aquamarine” can be produced but is uneconomical, and the one sold as such in the trades is in fact aquamarine-colored synthetic spinel. Aquamarine is brittle and sensitive to pressure.
Other guides relating to jewelry and gemstone buying which you may find helpful are as follows: