Crystals in volcanic rocks hold clues about when a volcano is about to blow, a discovery that could yield predictions about future eruptions, researchers say. Researchers writing in the journal Science say crystal formation can link the movement of underground magma to earthquakes, gas emissions and other warning signs to experts who monitor active volcanoes above ground, the Los Angeles Times reported. Formations known as orthopyroxene crystals form in magma when it\'s underground. Their chemical qualities depend on how hot the magma is, how much water or how many gas bubbles it contains, what sort of pressure the molten rock is under and what the magma is made out of in the first place, researchers said. \"Crystals are a bit like a book: If you know your alphabet you can read the book,\" vulcanologist Kate Saunders of the University of Bristol in England, who led the study, said. \"They provide a record for what happens. If we know what to look for and how to read them, we can work out the processes that formed the magma and how long it took these processes to occur.\" There\'s no easy way with current technology to sample underground magma in real time to look for signs of imminent eruptions, scientists point out, but finding a way to tell when a volcano is likely to explode remains the ultimate goal. \"If we can find a certain chemical signature that definitely heralds an eruption and we can see that also in a monitoring signal, that would be the Holy Grail,\" Saunders said.