Impala (natural stone)
.jpg)
Impala , mainly known as Nero Impala * , Nero Africa , Black Africa or Rustenburg in different variations and quality distinctions, as a natural stone that occurs in South Africa , is one of the plutonites (deep rocks). Rock classification: igneous, mafic, quartz-bearing gabbronorite with inverted pigeonite. In Europe it is assigned to the Gabbros family of rocks and is a norite in geology .
Breakdown and names
Impala is broken in South Africa near Rustenburg in South Africa's North West Province . The deposit is part of the Bushveld Complex .
The Impala rock has been mined since the late 1940s. In this area with numerous quarries , the world's largest raw block mining volume of hard rock is extracted. The mining area extends over a length of 70 kilometers from Rustenburg to Brits . The annual quarry volume in the entire quarry area is 140,000 to 150,000 m³ of tradable rough blocks. Only 10 to 12% of the extracted rock volume can be used as natural stone for further processing . While in the early years of mining the quarries and the resulting overburden were hardly recultivated and destroyed landscapes were left behind, this is said to have changed from the mid-1990s. Renaturation measures are primarily intended to initiate the large quarry companies.
Today (2015) the Marlin Group , a subsidiary of the Finstone Group , is the largest mining company there and operates ten quarries and employs 520 people. The Finstone Group , based in Luxembourg , claims to be one of the world's largest dealers of natural stone blocks. Marlin is technically able to mine around 70,000 m³ Impala stone blocks for the international market, the Kelgran 50,000 m³ and the small quarry companies 20,000 m³. According to the Marlin Group , it has mined around 45,000 m³ annually in the recent past. The Finstone group of companies differentiates in its own quarries according to color and mineralogical composition in quality groups. Modifications of the main group Nero Impala , which do not meet their quality standard, are called Nero Africo . Other suppliers assign further names according to their own specifications, which are incorrectly understood or traded as synonyms for Nero Impala . The composition actually varies considerably in the color and arrangement of the mineral structure, as well as their composition. The feldspar , which also causes the brown color in Nero Africo , is primarily responsible here . When laying larger quantities, care must be taken to ensure that the raw panels do not come from different quarries, as otherwise there may be annoying, clearly visible color differences and surfaces of different roughness, which could then be classified as no longer acceptable. For the reasons mentioned above, a warning must be given in particular against mixing raw panels with different trade names. A specific quality classification and precisely defined mineralogical compositions are only available from Nero Impala . With all other Impala variants, in many cases no precise material compositions and therefore no precise material properties can be named or queried. In these cases, extensive material examinations have to be carried out in which the mineralogical composition is determined by means of fine grinding and microscopic photographs.
There are various names in the trade for different Impala quality varieties, mostly Impala light or dark. The most common are Nero Africa and Nero Impala . Nero Impala has been protected as a trade name by the Marlin Group . The name of the stone types that can often be found in the trade by combining Nero Impala / with other Impala names has its origin in the lack of knowledge of the providers with regard to the above-mentioned quality differences and is also not permitted because the name Nero Impala is protected.
Occurrence, origin and composition
Norites are formed from metal-containing melts in the upper crust of the earth. The South African rock, which extends over an area of 66,000 km², is one of the largest such rock deposits. The rock was formed from an intrusion two billion years ago. This rock contains large ore deposits, the largest known deposit of platinum in the world, more than half of the global deposit of chromium and the world's largest deposit of vanadium . In the main zone of the Norit rock occurrence, which is located near Rustenburg, the Norites are extracted. The rock body reaches its greatest thickness at around 3000 meters .
Nero Impala consists of plagioclase (64%), orthopyroxene (30%), clinopyroxene (4%) and the accessories amphibole , chlorite , sericite and steatite . In the ore minerals, pyrite, chalcopyrite, ilmenite and magnetite are only found in this composition in Nero Impala . In the case of other impala varieties and other trade names, the compositions of the ore minerals sometimes differ, so that, for example, pyrrhotite is present instead of magnetite. The alteration is also more pronounced and the plagioclase is more clearly pigmented. In addition, the finest cracks can appear, which are filled with other minerals, such as carbonates, which in turn can be hygroscopic, i.e. react selectively and temporarily with liquids.
Technical characteristics and use
The minerals are distributed relatively evenly, so a uniform and even color impression is created. Impala has very good technical properties due to its even mineral distribution. Its distribution structure and its low thermal expansion predestine this stone for use as a base for technical measuring devices.
Originally, Impala was mainly used for making tombstones. A change set in and Impala has been used in the construction industry in recent years as flooring , stair covering , wall tiles , vanity and kitchen worktops and facade panels . Use as a polished stair or floor covering in heavily used areas (no problem in private areas!), Such as in public buildings, is not recommended. Not only because slip resistance becomes a problem with polished floor coverings, but polish losses occur relatively quickly. Impala has almost no quartz , one of the hardest minerals in rocks. It happens that in the Impala Africo the dark pyroxene minerals accumulate in individual places. One then speaks of "cat paws". They are not a technical defect, but a variety of nature, but are perceived as stains due to the rest of the uniform surface appearance and therefore usually represent an optical defect.
With regard to Nero Africa , a warning is issued against laying outdoors, as this variety can lead to staining. It is caused by magnetite crystals, which are converted by chemical processes when used outdoors and can then lead to rust discoloration and staining. Similar defects can also occur with some other Impala grades, because there is no reliable knowledge of the quality of the various trade names. The stones cannot be differentiated optically with regard to the internal quality even by experts simply by sighting, but would then have to be examined in the laboratory.
Web links
literature
- Karlfried Fuchs: Natural stones from all over the world, discover, determine, use. Vol. 1. P. 3, Callwey, Munich 1997, ISBN 3-7667-1267-5
Individual evidence
- ↑ a b c d Nero Impala (English). In: finstone.net. Retrieved March 15, 2015
- ^ I. Ashmole, M. Motloung (2008): Reclamation and Environmental Management in Dimension Stone Mining (English). S. 177. In: Surface Mining, ed. from The Southern African Institute of Mining and Metallurgy
- ↑ Quarries (English). In: neroimpala.com. Retrieved March 14, 2015
- ↑ Company Profile ( Memento of the original from February 19, 2015 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. (English). In: minaco.com. Retrieved March 15, 2015
- ↑ Finstone Group ( Memento of the original from April 2, 2015 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. (English). In: finstone.net. Retrieved March 15, 2015
