beryl
| beryl | |
|---|---|
 |
|
| General and classification | |
| chemical formula | Al 2 Be 3 [Si 6 O 18 ] |
|
Mineral class (and possibly department) |
Silicates and germanates - ring silicates (cyclosilicates) |
|
System no. to Strunz and to Dana |
9.CJ.05 ( 8th edition : VIII / E.12) 61.01.01.01 |
| Similar minerals | Chrysoberyl , apatite , spinel , brazilianite , tourmaline group |
| Crystallographic Data | |
| Crystal system | hexagonal |
| Crystal class ; symbol | dihexagonal-dipyramidal; 6 / m 2 / m 2 / m |
| Space group | P 6 / mcc (No. 192) |
| Lattice parameters | a = 9.22 Å ; c = 9.20 Å |
| Formula units | Z = 2 |
| Frequent crystal faces | {10 1 0}, {0001}, {11 2 0} |
| Twinning | rarely after {hk i l} |
| Physical Properties | |
| Mohs hardness | 7.5 to 8 (VHN - 1190 to 1450; average 1300) |
| Density (g / cm 3 ) | measured: 2.63 to 2.97; calculated: 2.640 |
| Cleavage | imperfect after {0001} |
| Break ; Tenacity | shell-like to uneven; brittle |
| colour | variable, often blue, green, yellow, pink, red, white, colorless |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass gloss to fat gloss |
| Crystal optics | |
| Refractive indices |
n ω = 1.568 to 1.602 n ε = 1.564 to 1.595 |
| Birefringence | δ = 0.004 to 0.007 |
| Optical character | uniaxial negative |
| Pleochroism | Faint to clear: ω = colorless, yellowish green to yellowish red , light blue ε = sea green, blue, red-violet |
Beryl is a frequently occurring mineral from the mineral class of " silicates and germanates ". It crystallizes in the hexagonal crystal system with the chemical composition Al 2 Be 3 [Si 6 O 18 ], that is an aluminum - beryllium silicate. Structurally it belongs to the ring silicates .
Beryl develops mainly large crystals with a tabular or prismatic to columnar habit and a glass-like to fat-like sheen on the surfaces. The largest known crystals were up to 18 meters long and weighed 180 tons. Beryl also occurs in the form of granular or massive aggregates , which are easily confused with quartz . In its pure form, beryl is colorless and transparent and in this form is known as goshenite . However, due to multiple refraction of light due to its polycrystalline design , it can also appear white and take on different colors due to foreign admixtures, whereby the transparency can decrease accordingly.
Due to its high Mohs hardness of 7.5 to 8 and its often well-developed crystals, beryl is mainly processed into gemstones , whereby the blue aquamarine , the green emerald and the light yellow to greenish-yellow golden beryl are known.
Etymology and history
The foreign word beryl was borrowed from the Latin beryllus or berillus and goes back through the Greek βήρυλλος [ béryllos ] to the Middle Indian ( Prakrit ) veruliya and ancient Indian ( Sanskrit ) vaiḍūrya . The latter is in turn derived from a Dravidian place name vēḷūr .
The Latin beryllus was used as a generic term for all clear crystals in the Middle Ages. From Middle High German berillus and berille , the word glasses (" eyeglasses ") arose because the first lenses were cut from crystal. The feminine singular die Brille is based on a later reinterpretation of the plural form die b [e] rille (singular der b [e] rille = single eyeglass) after two eyeglasses had become common.
The Latin berillus also derives Italian brillare (“shine, shine”) - and from it French briller , whose participle brillant (“shiny, radiant”) is based on the German foreign words brilliant (a specially cut diamond ) and brilliance . The English brilliant has the same origin. According to the common pronunciation, the English spelling would actually also be expected in German ( brilliant ). However, the norm (e.g. brilliant , brilliance ) in German is based on the French origin, which in this case leads to frequent spelling errors .
The mining of the beryl variety emerald can be traced back to the 13th century BC. Traced back to Egypt . But the gem was also widely traded in pre-Columbian South America .
classification
Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , beryl belonged to the mineral class of "silicates and germanates" and there to the department of " ring silicates (cyclosilicates)", where it was named after the "beryl group" with the system No. VIII / E.12 and the other members bazzite , cordierite , indialite , pezzottaite , secaninaite and stoppaniite .
The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also classifies beryl in the “ring silicates” section. This is, however, further subdivided according to the structure of the silicate rings, so that the mineral, according to its structure, can be found in the sub-section "[Si 6 O 18 ] 12− six-single rings without island-like, complex anions ", where the beryl group also gives it its name “With the system no. 9.CJ.05 and the other members Bazzit, Indialith, Pezzottait and Stoppaniit.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns beryl to the class of "silicates and germanates" and there in the category of "ring silicates: six rings". Here he is also the namesake of the "beryl group" with the system no. 61.01.01 and the other members Bazzit, Indialith, Stoppaniit and Pezzottait within the subdivision “ Ring Silicates : Six Rings with Si 6 O 18 Rings; possible (OH) and Al substitution ”.
Chemism
In 100% pure form, which can only be produced synthetically, beryl consists of around 19% aluminum oxide (Al 2 O 3 ), 14% beryllium oxide (BeO) and 67% silicon dioxide (SiO 2 ).
Natural beryl can contain various impurities such as rubidium oxide (Rb 2 O) and cesium oxide (Cs 2 O). Water of crystallization (H 2 O, up to 3%) as well as argon and helium can also be embedded in the channels of the ring silicate structure.
Other possible foreign admixtures include lithium and sodium as well as various oxides and hydroxides, halides and / or fluorides.
Crystal structure
Beryl crystallizes hexagonally in the space group P 6 / mcc (space group no. 192) with the lattice parameters a = 9.22 Å and c = 9.20 Å as well as two formula units per unit cell .
The crystal structure of beryl consists of six single rings with the structural formula [Si 6 O 18 ] 12− , which are concentrically stacked in the direction of the c-axis and each rotated by 30 °. Due to the concentric arrangement of the rings, open channels with a diameter of a few angstroms are formed . The various foreign admixtures are interchangeably stored in these hollow channels.
Between the rings, the aluminum - and Beryllium - ion , wherein aluminum and beryllium of six by four oxygen ions is surrounded. One speaks therefore of a [6] or [4] coordination in the case of aluminum or beryllium.
properties
morphology
The crystal morphology of beryl is predominantly simple and the costume is characterized by the hexagonal prism {10 1 0} and the final pinacoid {0001}. Occasionally there are also hexagonal-dipyramidal forms in the first and second positions {11 2 1} and {10 1 1} as well as the dihexagonal-dipyramidal full form ( holoedry ).
The habitus can be short to long prismatic, the prismatic surfaces often being striped lengthways. Occasionally there are stalky and granular to coarse masses.
physical and chemical properties
The melting point of beryl is 1650 ° C.
Beryl is insensitive to various acids and only slightly soluble in hydrogen fluoride (HF). On the other hand, it is sensitive to alkaline solutions and therefore soluble in sodium hydroxide (NaOH, caustic soda ) and potassium hydroxide (KOH, potassium hydroxide ).
Varieties and modifications
The colorless pure form of beryl, like the pure form of quartz ( rock crystal ), has its own name and is known as goshenite . Colorless beryls are very rare, however.
Far better known as colored varieties are the green emerald , the blue aquamarine , the yellow golden beryl (also heliodorus ) and the pink morganite , which was named after the New York banker John Pierpont Morgan (not to be confused with mogánite from the silica family ).
Another pink-colored, cesium- containing beryl variety is called vorobieffit , worobieffit or simply cesium beryl .
The variety of red beryl is also very rare , the outdated name of which, Bixbit, is one of the undesirable trade names according to the provisions of the CIBJO due to the clear risk of confusion with the mineral bixbyite .
faceted goshenite, 16.61ct, Brazil
Blue aquamarine from the Erongo Mountains , Namibia
faceted aquamarine, 13.24ct, Brazil
Dark green emerald from the Kagem Emerald Mine, Ndola , Zambia
faceted emerald, 1.07ct, Colombia
Golden beryl ( Heliodor ) from Marimbaia, Minas Gerais , Brazil
faceted heliodor, 48.75ct, Brazil
Pink morganite from the Darra-i-Pech pegmatite field, Nangarhar , Afghanistan
faceted morganite, 2.01ct, Brazil
Red beryl from the Harris Claim, Wah Wah Mountains, Beaver County, Utah , USA
Faceted Red Beryl / Bixbit, 0.56ct, Wah Wah Mountains, Beaver County (Utah) , USA
Zonal emerald to gold colored beryl from the Erongo Mountains, Namibia
Education and Locations
Beryl forms either magmatically in pegmatite and granite or hydrothermally in greisen or quartz veins. Also metamorphic formed beryl have been found, including gneiss . In addition, it can be enriched secondarily in the form of soap deposits in river sediments.
The accompanying minerals of beryl include albite , microcline , biotite , muscovite , lepidolite , quartz , fluorite , topaz , various tourmalines and ore minerals such as spodumene , amblygonite , cassiterite , tantalite (Mn) , tantalite (Fe) , columbite ( Mn) and columbite (Fe) .
Some of the many localities include Minas Gerais and Rio Grande do Norte in Brazil , Coscuez and Muzo in Colombia , Antsirabé in Madagascar , Spitzkoppe in Namibia , Iveland in Norway , Habachtal in Austria , Gilgit in Pakistan , Malyshevo and Murzinka in the Urals in the Russian Federation , Adun-Chilon in Siberia , as well as Keystone / South Dakota and Pala / California in the USA
Beryl crystals can grow to be extraordinarily large. For example, specimens six meters long and one and a half tons have already been found in the US state of Maine . Crystals up to 177 tons were found in Namivo / Alto Ligonha in Mozambique .
use
As a raw material
Beryl is the main source of the poisonous light metal beryllium , which is used in space technology as a component of special alloys. More than 80 percent of the world's annual production comes from the USA . In addition, beryls were cut into lenses in the Middle Ages, which were used as glasses and gave them their name.
As a gem
Beryls of all color varieties are processed into gemstones if they are of good quality . However, the emerald was one of the first varieties to be used for this purpose and was mined in larger quantities. The oldest mines can be traced back to around 1,300 BC. To date.
Clear gemstones are usually given a faceted cut . When grinding, however, the clear pleochroism of some beryl varieties must be taken into account.
Translucent or opaque stones are given a cabochon cut. Larger mineral aggregates are sometimes also made into handicrafts.
Others
"Beryl" is also a given name of women.
See also
literature
- Petr Korbel, Milan Novák: Encyclopedia of Minerals . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 .
- Walter Schumann: Precious stones and gemstones . 13th edition. BLV, Munich 2002, ISBN 3-405-16332-3 .
- Jaroslav Bauer, Vladimír Bouska, František Tvrz: The Cosmos Gemstone Guide . Kosmos Society for Friends of Nature, Franckh'sche Verlagshandlung, Stuttgart 1982, ISBN 3-440-04925-6 .
Web links
- Mineral Atlas: Beryl and Mineral Portrait (Wiki)
Individual evidence
- ↑ a b c d e Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 605 .
- ↑ Webmineral - Beryl (English)
- ↑ a b c d e f g h Beryl , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 68 kB )
- ↑ a b c d e f Hans Jürgen Rösler : Textbook of Mineralogy . 4th revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1987, ISBN 3-342-00288-3 , p. 541-543 .
- ↑ a b MinDat - Beryl (English)
- ↑ Keyword Brille in Kluge: Etymological dictionary of the German language . 24th edition
- ↑ See Beryl at Duden online
- ↑ Manfred Mayrhofer: Etymological Dictionary of the Indo-Aryan, Volume 2, Heidelberg: Universitätsverlag C. Winter, 1992, entry "vaiḍūrya-" (p. 588).
- ↑ See glasses at Duden online and Brill, m. and glasses, f. in Grimm: German Dictionary
- ↑ Entry 1 brilliant in Merriam-Webster online
- ↑ a b c Helmut Schrätze, Karl-Ludwig Weiner: Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 734-735 .
- ↑ Per Enghag: "Encyclopedia of the elements: technical data, history, processing, applications", Wiley-VCH Verlag, 2004, p. 350. ( limited preview in the Google book search).
- ↑ Richard V. Gaines, H. Catherine W. Skinner, Eugene E. Foord, Brian Mason , Abraham Rosenzweig: Dana's New Mineralogy . 8th edition. John Wiley & Sons, New York (et al.) 1997, ISBN 0-471-19310-0 , pp. 1240 .
- ↑ Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties . 5th completely revised and supplemented edition. Weise, Munich 2008, ISBN 978-3-921656-70-9 .