Accretionary Lapilli Tuff

Accretionary lapilli tuff is an igneous pyroclastic rock which is often formed when material produced by the volcanic activity is ejected into the air, although it can also be used to describe similar material which has been ejected and falls from the air during meteorite impacts as well. It is seen as more of a size distinction, with material between 2 – 64 mm being being lapilli, anything less is referred to as ash and anything greater volcanic bombs or blocks. These particular specimens how ever also exhibit an accretionary feature which is sometimes known as ‘birds eyes’. They appear as numerous elongated glassy dots on the surface of the specimens and are formed when volcanic particles in an ash cloud mix with moisture in the air which eventually form a sort of hailstone, composed mostly of ash and volcanic material, held together by moisture. As the particles get heavier, they fall downward onto the material below, creating a ‘dotted’ feature on the rock. These rock specimens come from Longsleddle, Cumbria,  in the UK. They are ideal for collectors due to their unique speckled feature and formation process, but also suitable for educational use of all levels as the samples are both informative for explaining volcanic processes to higher level students and intriguing for young students. Available in various sizes which you can choose from, and will come in a card tray with an information label.