Hardness of feldspar on the Mohs scale of hardness?
The hardness of potassium feldspar on the Mohs Scale of Hardness is a 6. The hardness of plagioclase feldspar is also a 6.
Schist is a composite material made up of a mixture of several minerals, each of which have different mohs hardness. Schist is made mostly of quartz (mohs 7) and feldspar (mohs 6) but also includes minerals such as chlorite (mohs 2) and hornblende (mohs 5). Schist has no real mohs hardness, but a composite of its constituents of approximately 6.