Printed from: https://conservationhandbooks.com/dry-stone-walling/know-your-stone/building-for-durability/
Choice of stone Characteristic walling stones are described in the following section, but a few general points are worth bearing in mind. Avoid highly fissile rock, good quality slate excepted. Fissile rock tends to split or fragment easily on weathering and so flakes away piece by piece. If it must be used, keep it in...