Definitions for "Rockwool"
This really is the state of the art rooting medium, and is used in plant propagation. It is alkaline and one will have to compensate for this.
a substrate used to grow plants hydroponically; an extruded wool-like product formed through a process of melting rock and extruding it into threads and pressing it into loosely woven sheets at high temperatures
inert, soil less growing medium consisting of thin strand-like fibres made from rocks