Aquamarine
| Aquamarine | |
|---|---|
 |
|
| General and classification | |
| chemical formula | Be 3 Al 2 [Si 6 O 18 ] + Fe 2+ and Fe 3+ |
|
Mineral class (and possibly department) |
see beryl |
| Crystallographic Data | |
| Crystal system | hexagonal |
| Crystal class ; symbol | see beryl |
| Physical Properties | |
| Mohs hardness | 7.5 to 8 |
| Density (g / cm 3 ) | 2.68 to 2.74 |
| Cleavage | indistinct |
| Break ; Tenacity | uneven, mussel-like |
| colour | pale blue to greenish |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices | n α = 1.564 to 1.569 |
| Birefringence | δ = 0.004 to 0.005 |
| Optical character | uniaxial negative |
| Axis angle | 2V = 0.014 |
| Pleochroism | clear: colorless, light blue, blue to blue-green |
| Other properties | |
| Chemical behavior | by hydrofluoric acid vulnerable |
Teal is the blue variety of silicate - Minerals beryl and therefore as well as these in crystallized hexagonal crystal system with the chemical composition of Be 3 Al 2 [Si 6 O 18 ].
The aquamarine gets its blue color from foreign admixtures of bivalent and trivalent iron ions (Fe 2+ and Fe 3+ ) on different grid positions . As an allochromatic (foreign colored) mineral, however, the color of the streak of aquamarine is always white. The shade named after the gem is a deep green-blue .
Due to its high Mohs hardness of 7.5 to 8 and its often well-developed, clear crystals , aquamarine is mainly processed into gemstones .
Etymology and history
The name aquamarine is derived from the Latin aqua marina "sea water" and thus refers to the pale blue to blue-green or "sea green" color of the mineral. In Europe, the color name for the blue beryl variety has been in use since the Renaissance (15th and 16th centuries).
Education and Locations
Aquamarines are found in pegmatites , especially in granites , but also in metamorphic rocks such as gneiss and as mineral soap in river sediments.
With around 660 known locations, aquamarine is a relatively common beryl variety with deposits on all continents (except Antarctica). The most important sites for commercial use as gemstones are mainly in Brazil , but also Nigeria , Kenya , Mozambique , Madagascar and Pakistan .
Like all beryls, aquamarine can often be found in the form of well-developed and transparent crystals, some of which are several decimeters in length and thickness. One of the largest crystals ever found is the greenish-blue and flawless aquamarine, discovered in 1910 on the Marambaia River in Brazil, with a size of 48 cm × 38 cm and a weight of 110.5 kg, or 520,000 carats . The largest and heaviest known crystal to date was discovered in 1992 in the Galilea mine near Governador Valadares in the Brazilian state of Minas Gerais and was one meter long and weighed 400 kg.
Use as a gem stone
Aquamarines are coveted gemstones that are offered in different cut shapes .
Particularly fine, deep blue aquamarines are labeled with the quality label “Santa Maria” (after the mine of the same name in Ceará , Brazil). The high quality “Santa Maria Africana” aquamarines, which are promoted in Mozambique , are based on this name .
The deep blue "Maxix Aquamarines" originally come from the Mina Maxixe on the Rio Jequitinhonha ( Minas Gerais , Brazil), are, in contrast to the "Santa Maria" aquamarines, not color-fast and gradually fade in sunlight and turn yellowish white. In the meantime, “Maxix-Aquamarines” colored deep blue by radioactive irradiation are also available, but these also fade over time and must be declared as treated in accordance with the provisions of the CIBJO .
Big and famous aquamarines
| Surname | Weight in carats | Found year | Found land | comment |
|---|---|---|---|---|
| "Marta Rocha" | 173,500 | 1954 or 1955 | on a farm near Teófilo Otoni , Brazil | Named after Miss Brazil from Rio de Janeiro at the time |
| "Quarto Centenario" | 110,000 | Brazil | ||
| "Estrela de Alva" or "Dawn Star" | 96,000 | Brazil | ||
| "Dom Pedro" | 10,395 | 1993 | Brazil | Was cut into an obelisk with wavy facets in Atelier Munsteiner , exhibited at the Smithsonian Institution since 2012 |
| No individual name known | 4,438 | Egg-shaped faceted aquamarine on display at the American Museum of Natural History in New York | ||
| "Eyvan Aquamarine" | 1,000 | 25 cm × 10 cm, greenish blue, faceted specimen on display at the Smithsonian Institution in Washington, DC |
Manipulations and imitations
Since the most sought-after color for gemstones (transparent, intense blue) is rarely found in nature, lower qualities are improved by firing between 400 and 450 ° C. Fired gemstones are difficult to distinguish from unfired and the “finishing” does not have to be specified when selling. However, fired stones are sensitive to the effects of heat and can sometimes lose color from around 100 ° C. Direct lighting from spotlights or sunlight can also have a detrimental effect on color quality.
Aquamarine is often imitated by synthetic quartz or spinel , but also by blue glass (trade name "Mass Aqua"). However, due to its lower hardness (e.g. Mohs hardness 5), glass can easily be distinguished from other gemstones.
Due to the similarities in color, blue elbaite ( indigolite ), topaz or zircon can be confused with aquamarine. However, indigolite and zircon are less hard and all three have a higher density than aquamarine (2.68 to 2.74 g / cm³).
See also
literature
- Christa Behmenburg, Maximilian Glas, Rupert Hochleitner, Michael Huber, Jan Kanis, Eckehard Julius Petsch, Karl Schmetzer, Stefan Weiß, Karl Egon Wild: Aquamarine & Co. the beryls aquamarine, goshenite, heliodor, morganite and red beryl . In: Christian Weise (ed.): ExtraLapis . tape 23 . Christian Weise Verlag, 2002, ISBN 3-921656-61-3 , ISSN 0945-8492 .
- Walter Schumann: Precious stones and gemstones. All species and varieties in the world. 1600 unique pieces . 13th revised and expanded edition. BLV Verlags-GmbH., Munich et al. 2002, ISBN 3-405-16332-3 , p. 110 .
Web links
- Mineral Atlas: Aquamarine and Mineral Atlas: Mineral Portrait Aquamarine (Wiki)
- Webmineral - Beryl (Aquamarine) (English)
- Mindat - Aquamarine (English)
Individual evidence
- ↑ a b c d e f Walter Schumann: Precious stones and gemstones. All species and varieties in the world. 1600 unique pieces . 13th revised and expanded edition. BLV Verlags-GmbH., Munich et al. 2002, ISBN 3-405-16332-3 , p. 110 .
- ↑ Christa Behmenburg, Maximilian Glas, Rupert Hochleitner, Michael Huber, Jan Kanis, Eckehard Julius Petsch, Karl Schmetzer, Stefan Weiß, Karl Egon Wild: Aquamarine & Co. the beryls aquamarine, goshenite, heliodor, morganite and red beryl . In: Christian Weise (ed.): ExtraLapis . tape 23 . Christian Weise Verlag, 2002, ISBN 3-921656-61-3 , ISSN 0945-8492 , p. 13 .
- ↑ Hans Lüschen: The names of the stones. The mineral kingdom in the mirror of language . 2nd Edition. Ott Verlag, Thun 1979, ISBN 3-7225-6265-1 , p. 174 .
- ↑ Mindat - Number of locations for aquamarine
- ↑ edelsteine.at: Aquamarine in the precious stone lexicon
- ↑ a b c d Mineralienatlas: Mineralienportrait Aquamarine
- ↑ a b carat-online.at: Gemstone Lexicon - Aquamarine
- ↑ a b c d All About Gemstones: Brazil, Minas Gerais - Gems & Minerals
- ↑ collectiongems.com: Gems International Ltd. - Aquamarine ( Memento from April 1, 2015 in the Internet Archive )
- ↑ smithsonianscience.org: Magnificent Dom Pedro aquamarine to go on view in the Smithsonian's Natural History Museum ( Memento of July 5, 2014 in the Internet Archive )
- ↑ Gem Etiquette - Aquamarine, Treatments
- ↑ Bernhard brother embellished stones . Neue Erde Verlag, 2005, ISBN 3-89060-025-5 , p. 44, 100, 103 .