|General and classification|
|chemical formula||Al 2 O 3 and additions of Cr|
(and possibly department)
|Crystal class ; symbol||see corundum|
|Density (g / cm 3 )||3.97 to 4.05|
|Break ; Tenacity||shell-like, uneven|
|transparency||transparent to opaque|
|shine||Glass gloss to diamond gloss|
n ω = 1.767 to 1.772
n ε = 1.759 to 1.763
|Birefringence||δ = 0.008 to 0.009|
|Optical character||uniaxial negative|
|Pleochroism||strong: yellowish red to deep carmine red|
As Rubin is called the red variety of the mineral corundum . The red discoloration is due to small amounts of chrome . Only the red corundum are called rubies, whereby the color can vary between pale red and dark red. Pink corundum, like blue and all other color varieties, are grouped under the name sapphire .
Etymology and history
Ruby is derived from the Middle Latin rubens, rubinus for red, the red .
It is believed that rubies were extracted from pits in what is now Myanmar and valued as early as the Bronze Age . Over 2000 years ago, rubies were also venerated in India and used as talismans . The ancient Egyptians , Greeks and Romans also knew rubies.
The ruby is already important in the Old Testament : it is the fourth of the twelve stones that adorn the high priest's efod, each of which is assigned a tribe of Israel . The ruby is the symbol of the royal tribe of Judah . Hrabanus Maurus writes that the ruby also shines in the dark and denotes the word of God. Alcuin said that the ruby denotes Christ. The lapidaries therefore presented the ruby as the “stone of stones”, which unites the “ forces ” of all other stones.
The red color of the ruby is due to the Cr 3+ ions it contains. Usually these cause a green color. In ruby, however, they occupy crystal lattice sites for the smaller Al 3+ ions, which increases the splitting of the ligand field in the chromium. The dd transitions responsible for the color therefore require more energy, so that shorter-wave light is absorbed, which is why the color appearance changes from green in Cr 2 O 3 to red in ruby. An additional storage of iron ions causes brownish tones.
The inclusion of rutile needles ensures special optical effects . If a few rutile needles are aligned parallel to a crystal axis, the stone appears cloudy to the eye, but has a silky sheen. In contrast, many rutile needles parallel to a crystal axis cause the so-called chatoyance or the cat's eye effect . Aligned parallel to the a-axes, the so-called asterism or star effect appears.
Education and Locations
For the conditions of formation of rubies see → Korund .
Rubies have been found on all continents except Antarctica , which is probably due to the ice cover. Usually only the Asian rubies are in demand . Myanmar , Thailand and Sri Lanka , with their increasingly rare deposits, are the most important countries for the export of these gemstones. In Asia there are many mines, especially in back India , but rubies have also been discovered in India , the People's Republic of China , Pakistan and Afghanistan . The East African rubies (e.g. Kenya and Tanzania ) also fetch high prices. There are only a few ruby finds on the continents of North America ( North Carolina / USA ), South America ( Colombia ) and Australia . In Europe , these gemstones were discovered in Finland , Greenland , Norway and North Macedonia .
In the 1960s, the valuable ruby mines were also discovered in East Africa .
Since 1835 it has also been possible to produce rubies artificially. For the manufacturing process, see → Korund .
As a gem
Rubies in a strong, red color and a bluish tinge, which is similar to the color of pigeon blood , are particularly sought-after and valuable . Color varieties that are weak in color or that play a brownish color are brought to stronger and more reddish colors by firing . Pink-colored corundum would count among the less valuable with the ruby designation and are therefore classified as sapphire. The trading center for Asian rubies is Bangkok .
Big and famous rubies
|Found year||Found land||comment|
|The Mogok Sun||1734.0||1993||Myanmar||to this day unsanded and untreated|
|Without proper name||250.0||in the Bohemian Wenceslas Crown|
|Edward Rubin||167.0||Exhibited in the British Museum of Natural History in London|
|Rosser Reeves ruby||138.7||Exhibited at the Smithsonian Institute in Washington|
|De-Long star ruby||100.3||Exhibited at the American Museum of Natural History in New York|
|Without proper name||40.6||Sold by Garrard & Co , London|
|Carmen Lúcia Buck||23.1||1930s||Myanmar||Exhibited at the Smithsonian Institute in Washington|
Manipulations and imitations
|"Adaleide Ruby", "American Ruby", "Australian Ruby"||Pyrope (garnet group)|
|"Balas Rubin"||pale red spinel|
|"Brazilian Ruby"||pink topaz|
|"Fake Ruby"||pink fluorite|
|"Montblanc Ruby"||Rose quartz|
|"Siberian Ruby"||red tourmaline|
Due to the similarity in color, ruby can be confused with various minerals such as red varieties of the garnet group and tourmaline group , fluorite , spinel , topaz and the reddish zircon variety hyacinth . Often these minerals, which are sometimes much cheaper than rubies, are also used to produce imitation rubies and are offered under mostly misleading trade names .
Already in the Middle Ages people tried to make artificial rubies.
In 1885 the first usable syntheses of rubies were brought onto the market in Geneva and sold as "real" (read: natural) rubies. The “Geneva Rubies” had the same density, hardness and optical properties as natural rubies, but could be exposed as synthetic melt products due to the numerous enclosed gas bubbles. At the same time, the French chemist Auguste Verneuil began his work on synthetic production. The procedure named after him was published by him only in 1902.
But even real, natural rubies are now mainly treated with different methods to improve their color. The preferred method is burning (up to 1950 ° C), whereby the stones are placed in borax or cryolite in order to fill the resulting cracks with a durable, glass-like material. Stones treated in this way can have a glass content of up to 20 percent by weight.
However, rough stones can usually be identified based on their typical prismatic and barrel-shaped crystal shape. In addition, there is often a significantly greater hardness than the mentioned minerals as an imitation base. Nevertheless, it is difficult for laypeople to distinguish, among other things, when it comes to doublets with a top made of natural corundum, synthetic ruby or other finished pieces of jewelry. It is possible to obtain a gemological report (certificate of authenticity) for valuable jewelry.
Ruby has long been used as a storage and pallet stone in high-quality clockworks . Further uses are the spherical tip on the stylus of coordinate measuring machines and the stylus of pickups for turntables (e.g. Ortofon "Kontrapunkt b", Benz "Ruby").
The doping element chromium is not relevant for mechanical applications, which is why it is equivalent to sapphire and corundum here.
In esotericism , rubies used to be the "stone of life and love". Storing this stone supposedly gave the owner more power, bravery and dignity. Rubies should protect against the devil and the plague . There is no scientific evidence for the alleged physical or psychological effects.
The fortieth anniversary of the wedding day is often referred to as the ruby wedding.
- Petr Korbel, Milan Novák: Encyclopedia of Minerals . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 82–83 ( Dörfler Natur ).
- 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. 98 .
- Rubin at www.mindat.org (Engl.)
- 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. 51 .
- De universo. Migne, Patrologia Latina 111, (1864) col. 471.
- Alcuin: Commentaria in Apocalypsin. Migne, Patrologia Latina 100, col. 1106.
- Paul Studer , Joan Evans: Anglo-Norman Lapidaries. Champion, Paris 1924, p. 89.
- Garrards - Treasures (large and important jewelry pieces) ( Memento July 29, 2012 in the Internet Archive ), accessed November 8, 2010
- Bernhard brother embellished stones. Recognizing imitations and manipulations in gemstones and minerals . Photos by Karola Sieber. Neue Erde, Saarbrücken 2005, ISBN 3-89060-079-4 , p. 95 .
- Walter Schumann: Precious stones and gemstones. All kinds and varieties. 1900 unique pieces . 16th revised edition. BLV Verlag, Munich 2014, ISBN 978-3-8354-1171-5 , pp. 101 .
- Anton Trutmann: Pharmacopoeia. (Hs. XI. 61 of the Burgerbibliothek Bern). Edition by Rainer Sutterer: Anton Trutmann's 'Pharmacopoeia', Part I: Text. Medical dissertation Bonn 1976, sheet 56 (“Ad faciendum preciosos lapides: Nim urinam de puero distillato; dar in solvier alun and leig christallum purum in it for four days. Dar still… suds in zinober, so we host a ruby”).
- Gemstone glossary: mixed cut - glyptics. Retrieved July 18, 2018 .
- Bernhard brother embellished stones. Recognizing imitations and manipulations in gemstones and minerals . Neue Erde, Saarbrücken 2005, ISBN 3-89060-079-4 , p. 93-94 .