Volcanic lapillus

Question: what are the characteristics of volcanic lapillus?

I would like to know what are the characteristics of volcanic lapillus

Volcanic lapillus: Answer: the lapillus

Dear Marianna,
the lapillus is the molten rock that comes out of the volcanoes, once it has cooled down from a friable rock, brown or reddish, rich in mineral salts, porous, used for a long time in gardening. It is an inert rock, which does not change the pH of the soil, and which does not add fertilizers, because, although it is rich in mineral salts, these dissolve in the soil very slowly. On the market there are various granulometries, from a few millimeters to about three centimeters, and the choice of the size of the grains depends on the intended use. The smaller and smaller grain sizes are in fact used to lighten and make more compact a compact soil, for example to be used with succulent plants in pots; the larger particle sizes instead are used instead of expanded clay, to be placed on the bottom of the pots, or as mulching, instead of barks. In fact, more and more often we see mulched flowerbeds with lapillus, which have a much better visual effect than those mulched with conifer bark. In fact, the function performed is identical to that of the cortex: shelter of the ground from insolation, isolation, weeding from weeds, greater quantity of humidity below the mulch. The lapillus is very suitable to be used in the flower beds, therefore, as mulching. Its use in the soil of plants is useful when it is intended to obtain a very well drained cultivation substrate, as in the case of succulents, or for citrus fruits. Instead of lapillus, perlite, pumice stone and pozzolana are used in the soil; it is not that one material is better than another, generally the less expensive and more readily available in the area in which we live is used.
As for the use of lapillus as a mulch, instead of barks, even here it is not that one is better than the other; it depends on the aesthetic taste, for example, in a Mediterranean garden, lapillus is certainly more pleasant than coniferous bark. Both materials are "ecological", in the sense that they are not produced with harmful chemical methods, the lapillus is simply collected from the slopes of the volcanoes, the barks are instead a waste of woodworking.