Image of the Day — Rapakivi syenite in the Gallinas Mountains

Rapakivi syenite sills intrude Permian limestone and sandstone along a closed road in the Gallinas Mountains, Lincoln County, New Mexico. The Finnish word “rapakivi” means disintegrated or crumbly rock or stone and denotes the tendency of certain rapakivi granite types to disintegrate more easily than other granitic rocks of southern Finland (type area of rapakivi granite). Rapakivi texture in the Finnish rapakivi granites is characterized by ovoidal alkali feldspar megacrysts mantled by sodic plagioclase and presence of short-prismatic quartz crystals.

For more information see our "Postcard from the Field" about these outcrops.