Rapakivi granite

As Rapakiwi is called Granite with unequal granular and up to several centimeters in size, round phenocrysts ( ovoids ) of feldspar and a relatively fine-grained matrix of quartz, various feldspars and Mafic Minerals.

Term

The term (Finnish rapakivi " crumbling stone " or "worse stone " ) is derived from the conspicuous weathering form. Local limited breaks the rock into sharp-edged debris. Solid stone and Gesteinsgrus are small areas next to each other. Jacob John Sederholm translated this common in southern Finland vernacular term in 1891 as a " rotten stone ".

The first mention of the name is found in U. Jerne and dates back to 1694th Daniel Tilas ( 1739 ), Böthlingk (1840 ) Thomas von Ungern -Sternberg (Leipzig 1882 dissertation), and Jacob John Sederholm (1891 ) attacked the terminus. The latter published his description in Tschermak 's Mineralogical and Petrographic releases of that year. Comes the first scientific description of this group of rocks according to modern understanding of this geologists.

Petrography, Typology

Besides the large ovoid the small crystals of the matrix fall on hard. However, they are still visible to the naked eye. The matrix has a special structure that is similar to the graphic granite and is called Myrmekit, even if it has a different origin cause. Small quartz crystals are grown through the larger feldspar crystals. In cross-section similar to this pattern old characters. Furthermore, the ovoids have often, but not always, a seam of plagioclase (eg green oligoclase ).

The Rapakiwigraniten two basic manifestations occurring after the crystalline structure can be distinguished. Two types is a porphyritic structure together, so that shows large single crystals in a much kleinkörnigeren matrix.

• Wyborgit (also Wiborgit )

• Pyterlit

Both variants, it is suitable that they have small drusen rooms. This feature is referred to as miarolitische cavities.

Dissemination

Rapakiwigranite are distributed worldwide, but mainly occur on geologically old continental crust of Precambrian age. The European main distribution area is located in Scandinavia, especially in Finland. The four Finnish Rapakiwiregionen are the Åland Islands, the region around Vyborg (some belonging to Russia), of Nystad and Pitkjaranta. Of prominent importance is the Vyborg Massif, a mittelproterozoischer batholith, which has been studied by Finnish and Russian scientists.

But even at the coast of north-eastern Sweden ( at Rödö ) in southern Norway ( Drammen ) and Russia ( Salminski solid and solid Uljalegski in South Karelia ), in the southern Urals and on the southwest coast of Lake Baikal ), there are Rapakiwi - rocks. Rapakiwis are also known from the Korean Peninsula and Ukraine.

In the Baltic region and in northern central Europe Rapakiwigranite can be found very often as glacial till. While they originated in the Baltics usually from Finland, the origin of most Rapakiwi -Attachment in Central Europe can be derived from the Åland Islands.

Rapakiwis than natural stone

Under the terms Baltic brown (or brown), Baltic red (or red), Carelian red red and Carmen are these rocks for decades as natural stone in use. It is widespread in Europe rocks for facades, floors, decorative objects and grave times.

Traditionally, due to rocks found in this type of architecture südfinnischer cities in the region and St. Petersburg again.