Duan stone is not sandstone?
Do the inkstone stone must be delicate, very coarse sandstone
Duan stone is divided into two categories, one kind of tone is purple, purple stone said, is rich in aluminum and iron, potassium, poor calcium silicate rocks, the main mineral water clay minerals in hydromica (containing partial crystal sericite) and a handful of dust like hematite, magnetite, quartz; another is green, green said, the main mineral is microcrystalline dolomite and a few hydromica, magnetite etc..
Duan stone is very delicate jade. Not sandstone, belonging to the accumulation of rock.
