Azul do Macaubas
Azul do Macaubas (often in short form: Azul Macaubas ) is the trade name of a stone from Brazil . In the geological sense it is a quartzite . This is a metamorphic rock. Occasionally this natural stone is also called the Azul Boquira .
Origin, location and composition
Azul do Macaubas was created from a quartz-rich sandstone that, under heat and pressure, transformed into a new rock, a quartzite, with completely different rock-technical properties. The age of its deposit is estimated to be around 1.2 billion years and it is classified in the Espinaço ( Precambrian ) stratigraphic group . The extraction sites are located to the west of the localities of Macaúbas and Boquira in the Brazilian Serra da Vereda countryside ( Bahia state ). The entire deposit extends over a length of 30 kilometers. The layers are up to 30 meters thick, but not all areas are suitable for mining. Fissures run through the deposit and have an unfavorable effect on the mining of rough blocks.
The reservoir conditions between Boquira and Macaúbas are accompanied by a variety of related and different rocks. For example, chlorite slate , biotitic mica slate , iron-shed quartzite , itabirite , amphibolite , dolomite and conglomerate occur.
In addition to the main component quartz, there is the coloring mineral dumortierite , an aluminum-iron-boron-silicate. That is why one speaks of a dumortierite quartzite in the petrographic sense. The natural stone typically contains 80% quartz , 15% dumortierite and up to 5% muscovite on average . Occasionally the blue mineral kyanite , magnetite and hematite is also represented.
The composition of the Azul Boquira variety is similar. It contains 85% quartz, 7% muscovite, 5% dumortierite and 3% kyanite.
Properties and use
This rock usually shows a sky-blue to white-blue wavy pattern and can (rarely) be colored blue in its entirety. Occasionally, isolated golden beige veins appear as a further structural feature. Slightly red-violet to brown-violet shades that come from a variety of the mineral dumortierite are also not untypical for good grades. The background can range from blue-gray to almost white.
There is no discoloration problem with Azul do Macaubas , as with other types of blue natural stone that contain the mineral sodalite . Installation in areas subject to permanent wetness is not recommended, as this stone partially contains the mineral sericite , a special type of muscovite mica. This can lighten to individual stains if it is permanently wet, which has already occurred in part due to natural processes.
Quartzites are rocks that are characterized by high abrasion resistance and this natural stone is particularly suitable for floor coverings , kitchen worktops , interior fittings / furniture parts, facades and art objects. In Magdeburg, a 5,500 m² facade of a commercial building complex made of Azul Macaubas was moved with a special fastening technology. In southern Europe it is occasionally used as tombstone material.
Usage examples
- Vienna , Graben 21, stele in the plastic group The four elements by Helmut Margreiter (1993), in front of the Erste Österreichische Spar-Casse-Bank building
- Magdeburg , Domplatz / Breiter Weg, facade (5,500 m²) of the commercial building of the Norddeutsche Landesbank ( Bolles + Wilson 2002)
Dismantling, sorting
The deposit is located in Brazil, in the state of Bahia near the city of Macaúbas and in the further north of Boquira.
Azul Macaubas is today (2008) one of the most expensive natural stones worldwide. In the international natural stone trade, exclusive types are traded at differentiated prices depending on their optical quality. With Azul Macaubas , the price differences per square meter can amount to several 100 euros, depending on the color purity and aesthetic structure. The sky-blue grades are very well known and in great demand. It is customary in international trade for the dark blue varieties to be referred to as Azul Boquira . Nevertheless, the generic term Azul Macaubas (more rarely: Azul do Macaubas ) has been in use for a long time and is quite appropriate.
For a long time this rock was considered the only stone with a significant dumortierite content. In the meantime, further deposits have been discovered in Madagascar and Mozambique (Siracaboe).
Azul Macaubas
(approx. 10 × 7 cm)
Azul Macaubas
(approx. 10 × 7 cm)
Azul Macaubas
(approx. 10 × 7 cm)
Azul Macaubas
(approx. 10 × 7 cm)
literature
- Karlfried Fuchs: Natural stones from all over the world, discover, determine, use . P. 143, Callwey, Munich 1997.
- Raymond Perrier: Les roches ornementales . Ternay (edition pro roc) 2004 ISBN 2-9508992-6-9
- R. Perrier / D. Aissaoui / B. Benziane: Les roches ornementales du Brésil . (in: Le Mausolée, No. 652) 1990
- José Vitorino de Souza: Contribução ao Estudo da Geologia da Formação Boquira (BA) . (Universidade Federal do Rio de Janeiro, Departamento de Geologia) 1975 (postgraduate script)
Web links
- Range of colors of the Azul do Macaubas
- Facade of the banking house Nord / LB from Macaubas in Magdeburg
Individual evidence
- ↑ Fastening technology for Macaubas panels ( Memento of the original from September 14, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ^ NordLB: NORD / LB Magdeburg . Data and images around the commercial building in Magdeburg. on www.nordlb.de
