Stone Chalk – Pulverised soft limestone from alpine rock forms.
Champagne Chalk – This name means a precise denomination of origin, because this chalk comes from the area around Reims (Champagne region).
Bologna Chalk – The name chalk is not entirely correct for this material, because it is a calcium sulfate (gypsum).
China-Clay – This is not a true chalk, but siliceous alumina (aluminum silicate), a weathering product of feldspar rocks.