Rapakivi

rapakivi

[¦rä·pə′kē·vē]
(petrology)
Granite or quartz monzonite characterized by orthoclase phenocrysts mantled with plagioclase. Also known as wiborgite.

Rapakivi

 

a granite of porphyroid structure with round phe-nocrysts of pink orthoclase surrounded by a white or light green shell of oligoclase. The granite consists of orthoclase (about 40 percent), oligoclase (about 20 percent), black mica (about 8 percent), idiomorphic quartz (about 30 percent), and secondary minerals (about 2 percent, including amphibole, orthite, sphene, diopside, magnetite, and apatite). Rapakivi is usually brownish pink or reddish; occasionally it is greenish or almost black.

The granite is common in Finland and Sweden. In the USSR it is found in the Karelian ASSR, in Leningrad Oblast (near the city of Vyborg), and in the Ukraine (near the village of Goro-dishche in Cherkassy Oblast). Rapakivi is a valuable building and facing stone. In Leningrad the columns of St. Isaac’s Cathedral are made of the granite, as is the facing of the banks of the Neva River.

References in periodicals archive ?
The adjoining building, 43 Temple Row, designed in 1980 by James A Roberts, the architect famous for the Rotunda and the Ringway Centre, is a brilliant composition in Rapakivi granite from Russia, travertine marble and Portland stone.
Emplacement and magnetic fabrics of rapakivi granite intrusions within Wiborg and Aland rapakivi granite batholiths in Finland.
and Lukkari, S.: 2005, Petrological and geochemical evolution of the Kymi stock, a topaz granite cupola within the Wiborg rapakivi batholith, Finland.
A close-up photograph of the outcrop along McDougall Inlet clearly shows pink megacrysts of potassium feldspar with rapakivi mantling characteristic of the Jimmy Hill Granite in contact with the equigranular John Lee Brook Granite (Fig.
Payolla, "Sn-polymetallic greisen-type deposits associated with late-stage rapakivi granites, Brazil: Fluid inclusion and stable isotope characteristics," Lithos, vol.
The Churio granite is pinkish, apparently fresh, leucocratic with rapakivi texture.
Among the crystalline basement rocks, the granites of the rapakivi formation cropping out on the bottom of the Gulf of Finland and in southern Finland are noteworthy.
It is greyish pink with porphidic to pegmatitic and rapakivi (K-feldspar phenocrystal up to 12 cm) textures.
postdating the Svecofennian orogeny, and anorogenic Palaeo-Mesoproterozoic Rapakivi Province magmatism (Koistinen et al.