Onsernone rock is a homogeneous gneiss with a dark grey colour, fine grain and marked schistosity. It is extracted near Vergeletto, a municipality in the Onsernone Valley in the canton of Ticino (Switzerland), which is where this gneiss gets its name. Specifically, it has the following composition: approximately 30% quartz, approximately 35% feldspar (plagioclase, with a small amount of potassium feldspar), approximately 20% biotite (dark mica) and approximately 12% epidote (clinozoisite), with approximately 2% titanite and approximately 1% zircon as accessories.This gneiss is highly resistant to frost, acids and alkalis.
References for use of the material
Bagni di Craveggia, Elena Bonardi, Craveggia (Italy).
Main source of description
Material-Archiv. (2023). Onsernone.
Original source of characteristic values
