We provide new insights into the release of H₂O from the phonolitic melt of the Laacher See volcano. Decompression experiments conducted at superliquidus conditions revealed uniformly dispersed vesicles throughout the samples, with extremely high vesicle numbers regardless of the decompression rate. These findings enhance our understanding of volcanic eruptions and might suggest that rapid volatile release due to off-critical spinodal decomposition increases explosive volcanic activity.

As magma ascends, H₂O-supersaturated melt forms fluid vesicles, creating high vesicle number densities (VNDs) and increasing melt porosity, accelerating magma ascent. This study examines how VNDs vary with decompression rate as vesicles begin to coalesce. The shift from decompression-rate-independent to decompression-rate-dependent VND can strongly influence eruption styles, creating permeable channels or forming closed-porosity foams that trap pressurized gas, potentially leading to explosive eruptions.

An unusual tourmaline was studied using a multi-analytical approach. The sample comes from a granitic pegmatite on the island of Elba and consists of three generations of tourmaline: green prismatic tourmaline, a dark fibrous cap, and colourless acicular single crystals. The most likely scenario for its formation involves the miarolitic cavity fracturing due to mechanical shock, the subsequent circulation of the highly reactive cavity fluids, and the leaching of accessory biotite in the surrounding pegmatite.