Fragmental

These are similar in composition to the leaner iron ores of Brazil, called itabirite, but differ in that the silica is in the form of chemically deposited chert, rather than fragmental quartz grains.

However, the most common killer in fatal eruptions is tephra, which includes all fragmental material thrown from volcanoes, killing mainly by collapse of ash-covered roofs (the most deaths) or by projectile impact (by far the largest number of fatal tephra accidents).