Pumice stone 3/7mm (approx 1kg - 1.5Lt) Pumice and lapilli are the product of explosive volcanic eruptions resulting from a violent expansion of gases dissolved in lava with acidic chemical composition: the rapid cooling of the rock prevented its crystallization, retaining the gases inside, and generating minerals that spread in a stronger expansion of the alveoli or less less acccent. In fact, during the solidification phase, the vapors present in the magma that were suddenly released caused the swelling of the entire magma mass, and during this rapid cooling phase the differences in the physical structure of the various volcanic aggregates were determined: the volcanic lapillas were formed from a magma with a lower silicon dioxide content. The lower viscosity and slower cooling of the lava have facilitated the escape of a certain amount of the gases present in the magma. Minerals formed which were characterized by emptiness with an average diameter larger than that of pumice but had a significantly lower number. MEDIUM CHEMICAL ANALYSIS SiO 2: 62.5% Al 2 O 3: 17.5% K2O: 9.5% Fe 2 O 3: 2.6% CaO: 2.5% Na 2 O: 2.2% TiO 2: 0.5% MgO: 0.4% TECHNOLOGY NISCHCHNNNShafts pH: 6.5 - 7.0; cation exchange: 30 meq / 100 g. Functional features and areas of use: light natural inert, ideal for: ? Root substrate (sowing, cuttings, transplants, soilless plants and hydroponics); ? Making universal moulds; ? Preparation of specific soils (annuals, acidophilic plants, succulents, indoor plants, lawns? ); ? Preparation of professional soils for horticultural gardeners