scoria - teaching hand specimen of maroon/red scoriaceous basalt from Mauna Loa volcano
This red scoriaceous basalt was collected from a quarry at about 10,500 feet on the north slope of Mauna Loa, Hawaii. Blocks and scoria associated with a satellite cinder cone were used as the road base for the road that leads to the NOAA weather observatory at an elevation of 11,140 feet.
Scoria is the silica poor equivalent of pumice. Lava with a low silica content is runny, so gas bubbles tend to coalesce to form larger bubbles in basalt. In a silica rich granitic magma, high viscosity prevents bubbles from coalescing, so there are many more, but smaller, thin-walled gas bubbles in pumice, one reason it floats longer in water.
This scoria surprisingly light and most is amazingly red from the oxidation of hematite. Its viscosity was low when thrown from the vent and it almost looks molten. Any student would identify it as lava. These hand specimens particularly light weight, reinforcing to students that scoria is the silica poor equivalent of pumice.
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