Editing Lapilli (section)

===Accretionary lapilli===
[[File:Accretionary Lapilli - geograph.org.uk - 831917.jpg|thumb|Accretionary lapilli in the [[Mesoproterozoic]] [[Stac Fada Member]] of the [[Torridonian]], of probable impact origin]]
Rounded balls of [[tephra]] are called ''accretionary lapilli'' if they consist of layered [[volcanic ash]] particles.  Accretionary lapilli are formed by a process of wet [[Volcanic ash aggregation|ash aggregation]] due to moisture in volcanic clouds that sticks the particles together, with the volcanic ash nucleating on some object and then accreting to it in layers before the accretionary lapillus falls from the cloud.  Accretionary lapilli are like volcanic hailstones that form by the addition of concentric layers of moist ash around a central nucleus.

This texture can be confused with [[spherulite|spherulitic]] and [[axiolitic]] texture.

====Armoured (or cored) lapilli====
These lapilli are a variety of accretionary lapilli, though they contain lithic or crystal cores coated by rinds of coarse to fine ash.  Armoured lapilli only form in hydroclastic eruptions, where significant moisture is present.  The vapour column contains cohesive ash which sticks to particles within it.