- Greenschist (Wikipedia)
Greenschists are metamorphic rocks that formed under the lowest temperatures and pressures usually produced by regional metamorphism, typically 300–450 °C (570–840 °F) and 2–10 kilobars (29,000–145,000 psi). Greenschists commonly have an abundance of green minerals such as chlorite, serpentine, and epidote, and platy minerals such as muscovite and platy serpentine. The platiness gives the rock schistosity (a tendency to split into layers). Other common minerals include quartz, orthoclase, talc, carbonate minerals and amphibole (actinolite).
- Whetstone River (Wikipedia)
The Whetstone River is a 12.7-mile-long (20.4 km) tributary of the Minnesota River, in northeastern South Dakota and a very small portion of western Minnesota in the United States. Via the Minnesota River, it is part of the watershed of the Mississippi River.