Neither aggregate nor sandy microstructures
In vughs. No separated aggregates. Groundmass broken by vughs, but not interconnected, with some channels and chambers.
In channels. No separated aggregates. Groundmass broken by dominant channels.
In chambers. No separated aggregates. Groundmass broken by dominant chambers.
Vesicular. No separated aggregates. Groundmass with dominant vesicles.
Spongy. Few, if any, aggregates. Abundant voids, closely interconnected.
Fissured. Few, if any, fully separated aggregates, with many interconnected fissures.
Cracked. No fully separated aggregates, dense material with only a few cracks (and channels).
Massive. No separated aggregates, very dense material, with hardly any voids.
Sand grain microstructures