Cavasite [Ca(VO|Si4O10) · 4H2O] on stilbite (Desmin) [(Ca,Na,K)4-5(Al,Si)18O36 · 14H2O]

Gas bubbles often form in cooling lava and cannot escape. If water loaded with minerals enters these cavities, a wide variety of minerals can crystallize out of them over time. The cavities incompletely filled with crystals are called druses. Druses with a special mineralization of white stilbite and blue cavasite have become famous from the basalts of the Indian state of Maharashtra.