Last updated: August 18, 2024
Place
Stop #5: Pegmatite
NPS Photo
Quick Facts
Location:
43.592578, -103.487203
Significance:
Black Hills pegmatite is among some of the oldest exposed rocks in the world.
Amenities
2 listed
Parking - Auto, Parking - Bus/RV
Geologic age: Precambrian
Continue north on route 87 for 1.8 miles. The pegmatite is found at a parking area on the right side of the road with a wayside exhibit titled Ancient Foundations.
Pegmatite is part of the Precambrian core of the Black Hills. It is an extremely coarse grained igneous rock that formed deep within the earth. The large crystals indicate that it cooled very slowly.
Look for three common minerals in pegmatite: quartz (greasy looking), feldspar (pink with shiny flat surfaces), and tourmaline (black with long, slender crystals).
Continue north on route 87 for 1.8 miles. The pegmatite is found at a parking area on the right side of the road with a wayside exhibit titled Ancient Foundations.
Pegmatite is part of the Precambrian core of the Black Hills. It is an extremely coarse grained igneous rock that formed deep within the earth. The large crystals indicate that it cooled very slowly.
Look for three common minerals in pegmatite: quartz (greasy looking), feldspar (pink with shiny flat surfaces), and tourmaline (black with long, slender crystals).