Aquamarine.

Color: Light blue, blue, blue-green
Chemical composition:  Al2Be3(Si8O18) aluminium beryllium sliciate
Mohs’ hardness: 7 ½-8
Transparency:  Transparent to opaque
Luster: Vitreous
Fracture:  Conchoidal, uneven, brittle
Crystal system:  Hexagonal (trigonal); long prisms
Cleavage:  Imperfect
Specific gravity:  2.67-2.71
Refractive index:  1.577-1.583
Dispersion: 0.014
Pleochroism: Definite, nearly colorless-light blue
Fluorescence:  None
Occurrence:  Afghanistan, Australia, Brazil, India, Kenya Malagasy Republic, Myanmar, Nigeria, Pakistan, Russia, Sri Lanka,  and the United States (Colorado).
Astrology:   March birthstone, connected to Pisces;  prior to the 15th century, it was the October birthstone
Chakra:  5th (throat), and helps align the chakras

Aquamarine, like emerald, heliodor, and morganite, is part of the beryl group.   Its name, which means “water of the sea” comes from the Latin words aqua (water) and mare (sea).   Most aquamarines are found in granite pegmatites, which form as liquid molten rocks that rise through fissures and cracks in the Earth’s crust.   The stone’s distinctive blue comes from traces of iron interacting with light.   Brazil is currently the prime source for aquamarines.  Extraordinary crystals have been found there, including a 550,000-carat  aquamarine crystal that was found in 1910.  Though, sky-blue and dark blue stones are now the most highly prized, in the 19th century, sea-green stones were preferred.  Most aquamarines today are heat-treated, which removes the green hues, resulting in a purer blue.
It wasn’t until the 1600s that the stone was actually called aquamarine.  Before that it was known as “sea-green beryl.”   The Roman naturalist Pliny, who lived from 23-79 A.D., referred to it as a remedy for eye disease.  More poetically, an ancient legend claimed that aquamarines were taken from the treasures chests of sea nymphs and carried to the shore by seahorses.  Sailors wore aquamarines as amulets, believing that the stone would ensure that they would cross the sea and return home safely.   Known as a “stone of courage,” aquamarine was also believed to give ocean travelers courage for the journey; it was believed that the stone’s powers strengthened when it was immersed in water. Aquamarine was also said to carry the energy of young love, and bring good things to those in love.  Husbands gave it as love token to their wives, after the marriage was consummated.  Dreaming of the stone was said to bring new friends in one’s life.
From the Middle Ages through the Renaissance, aquamarine’s pale blue color was connected with the moon and said to be subject to lunar influences.  Considered most powerful during full moon, aquamarine was used for crystal gazing and finding lost objects. Aquamarine amulets were worn to grant  invulnerability in battle and in legal disputes, and the stone was used to revive fading love in a marriage.  Medicinally, it was used to treat toothache, digestive troubles, swollen glands, and liver and eye disease. Aquamarines were also loved by those drawn to the occult.  It was considered sacred to the goddesses of the sea, and sea witches were said to cleanse the stone in the sea beneath a full moon and use them as a protection for flying over water.  Nowadays in magical practice, aquamarines are used for purification before rituals, and are sometimes exchanged between lovers for a good relationship. The crystals are also said to strengthen psychic abilities, protect against storms (particularly if placed in a suitcase before a journey), and bring good health. Metaphysical beliefs draw on some of the older ones.  Aquamarine is still considered a stone of courage, and a stone that will enhance psychic powers.  It’s said to be particularly helpful in meditation, opening you to intuition and clairvoyance.   It’s also a stone of clarity, and when placed on the throat chakra, it may help with communication.  In healing work, aquamarine is said to boost the immune system. The gentle blue of aquamarine combines beautifully with pearls, rose quartz, peridot, pink or white coral, pink or green tourmaline, golden topaz, green jade, or a lavender amethyst.  For contrast, try black onyx or labradorite.   And for a lovely summery piece, combine aquamarine with pearls, smoky quartz, and  blue-green chalcedony or chrysoprase. While aquamarine is not as brittle as emerald, it can be damaged by ammonia, acids or heat, or ultrasonic cleaners.  To clean aquamarines, use gentle soap and lukewarm tap water.