is a hornblende-biotite granite
containing large rounded crystals of orthoclase
mantled with oligoclase. The name has come to be used most frequently as a textural term where it implies plagioclase
rims around orthoclase
in plutonic rocks. Rapakivi is Finnish for rotten or crumbly rock and describes the tendency of the rapakivi granite
to easily weather.
Rapakivi is a fairly uncommon type of granite
, mostly found in southeastern Finland. It can also be found e.g. on Åland, in Laitila in southwestern Finland, and in some parts of Sweden.
Rapakivi is the material used in Ålands Middle Age stone churches.
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