On the surface it looks just like a fine sand but unlike sand there must be something about the micro-structure of this material that holds much more water than expected.
Pore space for water holding and cation exchange.
palagonitic dust, which contains hydrated and hydroxylated volcanic glass of basaltic composition, accommodates significantly more H2O under comparable humidity and temperature conditions than do the smectites nontronite and montmorillonite.
What’s in Palagonite?
How is it formed?
Does it make a good soil amendment?
Overview of Palagonite for Organic Farming
Personally, when used as a soil amendment, I’d prefer something with lower levels of Aluminium Oxide and Titanium Dioxide, Sodium Oxide is borderline too, but you can’t argue with the results when mixed with compost.
Composting with Palagonite: