Korpilahden musta dioriitti, Korpilahti Black

Korpi Black diorite from the Muurame-Korpilahti area.

The diorites are composed of 60-80% plagioclase and a total of 20-40% biotite, hornblende and pyroxene, sometimes with a few percent of quartz. They are dark grey or almost black in colour and their mineral grains are typically less than 5 mm in diameter and occasionally distinctly oriented.