What’s horticultural grit made from?
RA Quinn, by email
A CHRISTINE SAYS Normally it is either made from crushed granite or limestone and is crushed to be 1-4 mm in size. The granite is acidic in nature; the limestone grit is alkaline and they should be used accordingly. Neutral pH grit is also available. The particles should be angular not round. It improves aeration and may be used for insulation.