igneous
Rapakivi granite
Rapakivi granite, a granitic intrusive rock composed chiefly of alkali feldspar, plagioclase, quartz, and biotite
AI-generated identification · may be incorrectPink, coarse-grained rock with distinctive rounded feldspar crystals and pale plagioclase rims; minerals are mostly Mohs 6–7, with vitreous quartz and blocky feldspar cleavage. The pictured cut surfaces show the characteristic texture.
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Physical properties
Pink, coarse-grained rock with distinctive rounded feldspar crystals and pale plagioclase rims; minerals are mostly Mohs 6–7, with vitreous quartz and blocky feldspar cleavage. The pictured cut surfaces show the characteristic texture.
Formation & geological history
Formed when granitic magma cooled slowly underground, allowing large feldspar crystals to grow; rapakivi granites are chiefly Precambrian, commonly about 1.6–1.7 billion years old.
Uses & applications
Used as dimension stone, monuments, paving, and decorative slabs; attractive specimens are collected and displayed.
Geological facts
“Rapakivi” comes from Finnish for “crumbly rock.” The large, rounded feldspar crystals, often rimmed by plagioclase, are termed rapakivi texture.
Field identification & locations
Recognize it by pink rounded feldspar megacrysts with contrasting rims set in a coarse quartz-feldspar matrix. Classic occurrences are in Finland and the Baltic region; similar rapakivi granites occur elsewhere.
