Beryl - Be3Al2(Si6O18)

The beryl structure contains hexagonal rings of sic SiO4 tetrahedra, with the ring stacked vertically such that the hexad symmetry axis becomes the c crystallographic axis. The hexagonal rings are joined by Be2+ and Al3+ cations in four- and sixfold coordination.

The name beryl is derived from Greek beryllos which referred to a precious blue-green color-of-sea-water stone The first eyeglasses constructed in 13th century, in Italy, were made of beryl as glass could not be made clear enough.
Beryl is a characteristic mineral of silica-rich granites and granitic pegmatites, in association with quartz, alkali feldspar and muscovite.

Varieties

Aquamarine (from Latin: aqua marina, water of the sea) is a blue or cyan variety of beryl. The pale blue color of aquamarine is attributed to Fe2+.
Emerald is green beryl, colored by trace amounts of chromium and sometimes vanadium.
Golden beryl and heliodor The golden yellow color is attributed to Fe3+ ions. heliodor (from Greek helios, sun, and doron, gift) is a greenish-yellow variety of beryl.
Maxixe (pronounced mashish) is a very rare dark blue beryl. The dark blue color is thought to be developed in the ground by exposure to natural radiation. Maxixe is an unfortunate material because the wonderful blue color quickly fades in daylight to a pale brownish yellow color. The color can be restored with additional irradiation, but that color is also quickly lost with exposure to light. Maxixe was first found in 1917 in a mine in the Minas Gerais area of Brazil. It has since been found in small amounts at a few other locations.
Goshenite is the colorless variety of beryl. The name originates from Goshen, Massachusetts, where it was originally discovered. Goshenite is the purest variety of beryl.
Morganite also known as pink beryl, rose beryl, is a rare light pink to rose-colored gem-quality variety of beryl. The pink color of morganite is attributed to Mn2+ ions.
Red beryl (formerly known as bixbite and marketed as red emerald is a red variety of beryl. It was first described in 1904 for an occurrence, its type locality, at Maynard's Claim (Pismire Knolls),Utah. The dark red color is attributed to Mn3+ ions.


Optical Properties:
Form: Crystals tend to be euhedral, with hexagonal basal section and rectangular prismatic sections, and range from microscopic needles to huge crystals weighing tons.
Relief: Moderate.
Cleavage: Imperfect.
Fracture: Conchoidal to uneven.
Color: commonly colorless in thin section.
Pleochroism: Weak to distinct, from colorless, yellowish green, light blue, yellowish red to sea-green, blue, purplish red.
Interference colors: Very low (I order black-gray-white).



Bibliography



• Deer, W.A., Howie, R.A., Zussman, J. (1998) Rock-forming Minerals.
• Optical Mineralogy : The Nonopaque Minerals by Phillips / Griffen
• E. WM. Heinrich (1956): Microscopic Petrografy. Mcgraw-hill book company,inc
Stephen. A. Nelson


Photo Foto
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Beryl (high relief, light gray) in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. PPL image , 2x (Field of view = 7mm)
beryl(2).jpg

Beryl (dark gray) and plagioclase in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. XPL image , 2x (Field of view = 7mm)
beryl(3).jpg

Beryl (dark gray) and plagioclase in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. XPL image , 2x (Field of view = 7mm)
beryl(4).jpg

Beryl (high relief, light gray) in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. PPL image , 2x (Field of view = 7mm)
beryl(5).jpg

Beryl (dark gray) and plagioclase in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. XPL image , 2x (Field of view = 7mm)
beryl(6).jpg

Beryl (high relief, light gray) in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. PPL image , 2x (Field of view = 7mm)
beryl(7).jpg

Beryl (dark gray) and plagioclase in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. XPL image , 2x (Field of view = 7mm)
beryl(8).jpg

Beryl (high relief, light gray) in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. PPL image , 2x (Field of view = 7mm)
beryl(9).jpg

Beryl (dark gray) and plagioclase in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. XPL image , 2x (Field of view = 7mm)
beryl(10).jpg

Beryl (high relief, light gray) in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. PPL image , 2x (Field of view = 7mm)
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Beryl (dark gray) and plagioclase in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. XPL image , 2x (Field of view = 7mm)
beryl(12).jpg

Beryl (high relief, light gray) in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. PPL image , 2x (Field of view = 7mm)
beryl(13).jpg

Beryl (dark gray) and plagioclase in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. XPL image , 2x (Field of view = 7mm)
beryl(14).jpg

Beryl (dark gray) and plagioclase in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. XPL image , 2x (Field of view = 7mm)
beryl(15).jpg

Beryl (high relief, light gray) in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. PPL image , 2x (Field of view = 7mm)
beryl(16).jpg

Beryl (dark gray) and plagioclase in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. XPL image , 2x (Field of view = 7mm)
beryl(17).jpg

Beryl (high relief, light gray) in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. PPL image , 2x (Field of view = 7mm)
beryl(18).jpg

Beryl (dark gray) and plagioclase in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. XPL image , 2x (Field of view = 7mm)
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Beryl (high relief, light gray) in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. PPL image , 2x (Field of view = 7mm)
beryl(22).jpg

Beryl (dark gray) and plagioclase in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. XPL image , 2x (Field of view = 7mm)
beryl(23).jpg

Beryl (high relief, light gray) in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. PPL image , 2x (Field of view = 7mm)
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Beryl (dark gray) and plagioclase in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. XPL image , 2x (Field of view = 7mm)
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Beryl (dark gray) and plagioclase in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. XPL image , 2x (Field of view = 7mm)
beryl(26).jpg

Beryl (dark gray) and plagioclase in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. XPL image , 2x (Field of view = 7mm)
beryl(27).jpg

Beryl (high relief, light gray) in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. PPL image , 2x (Field of view = 7mm)
beryl(28).jpg

Beryl (high relief, light gray) in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. PPL image , 2x (Field of view = 7mm)
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Beryl (dark gray) and plagioclase in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. XPL image , 2x (Field of view = 7mm)
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Beryl (high relief, light gray) in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. PPL image , 2x (Field of view = 7mm)
beryl(33).jpg

Beryl (dark gray) and plagioclase in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. XPL image , 2x (Field of view = 7mm)
beryl(35).jpg

Beryl (high relief, light gray) in a granitic pegmatite from Rio Masul, Passiria Valley, Bolzano Province (South Tyrol), Italy. PPL image , 2x (Field of view = 7mm)